Physics A2 Temp UP TO DATE (EXCLUDING MAGNETIC FIELDS) For printing

(Equation +) Give two equations relating angular velocity, time period and frequency. Explain how they are formed

(Based on f = 1/T) For a complete circle an object turns through 2π radians in a time T, so frequency and period are related by the following equations: ω = 2π/T and ω = 2πf

How would you setup an experiment to measure the Specific Heat Capacity of a solid? What about with a liquid? (1/2)

(See Diagram on page 6) 1. Use electric heater, digital thermometer, insulating material and a solid. 2. Similar setup but with a heating coil instead of a electric heater if you wish, and an insulating lid on top.

Make sure you know how to use radians

(See page 14)

Give the history of the universe at 10⁻⁴ seconds

(We are now on more solid ground) 1. This corresponds to a temperature of around 10¹² K. 2. The universe is cool enough for quarks to join up to form particles like protons and neutrons - they can never exist separately again. 3. Matter and antimatter annihilate each other, leaving a small excess of matter and huge numbers of photons (resulting in the cosmic background radiation that we observe today).

(Equation +) Describe and explain Boyle's law, giving the equation. (See graph on page 8)

1 At a constant temperature, the pressure p and volume V of a gas are inversely proportional. 2. (The higher the temperature of the gas, the further the curve is from the origin) Equation: pV = Constant or Pressure x Volume = Constant

Explain what Ultrasound waves are, and the frequency of those used for medical purposes

1 Longitudinal waves with higher frequencies than humans can hear (>20 000 Hz) 2. For medical purposes, frequencies are usually from 1 to 15 MHz

Relate v and MeV

1 MeV = 1.6 x10⁻¹³ V

Explain the link between nucleon number and the size of an atom

1. (As you know from other cards) the particles that make up the nucleus (i.e. protons and neutrons) are called nucleons. The number of nucleons in an atom is called the nucleon (or mass) number, A. 2. As more nucleons are added to the nucleus, it gets bigger (unsurprisingly).

Explain what Capacitors are and what they are made up of

1. A capacitor is an electrical component that can store electrical charge 2. Capacitors are made up of two conducting plates separated by a gap or a dielectric (an insulating material)

What are the 2 key numeric points for converting between Celsius and Kelvin?

1. A change in 1 K = a change in 1°C 2. To change from Celsius into Kelvins you simply add 273

What does a Maxwell-Boltzmann graph show?

1. A graph of the numbers of molecules in a gas with different kinetic energies 2. It is a theoretical model which has been developed to explain scientific observations.

Explain how Mases in a Gravitational Field experience a Force of Attraction

1. A gravitational field is a force field - a region where an object will experience a non-contact force. 2. Force fields cause interactions between objects or particles - e.g. static or moving charges interact through electric fields and objects with mass interact through gravitational field. 3. Any objects with mass will experience an attractive force if you put in the gravitational field of another object. 4. Only objects with a large mass, such as stars and planet have a significant effect. E.g. the gravitational fields of the Moon and the Sun are noticeable here on earth - they're the main cause of our tides.

State Kepler's Second Law See diagram on page 27

1. A line joining the Sun to a planet will sweep out equal areas in equal times 2. (So if moving from A to B takes the same amount of time as going from C to D, the two shared sections will have equal areas.

Explain the energy released during nuclear fusion

1. A lot of energy is released during nuclear fusion because the new heavier nucleus has a much higher binding energy per nucleon (and so a lower total mass, see other cards). 2. The energy released helps to maintain the high temperatures needed for further fusion reactions

What are molecules? What does their size roughly equal?

1. A number of atoms joined together. 2. Roughly, their size equals the number of atoms in it multiplied by the size of one atom.

Explain the Photoelectric Effect as a way of attenuating X-rays

1. A photon with around 30 keV of energy is absorbed by an electron, which is ejected from its atom 2. The gap in the electron shell is filled by another electron which emits a proton

What are satellites?

1. A satellite is just any smaller mass which orbits a much larger mass - the Moon is a satellite of the Earth 2. In our Solar System, the planets have nearly circular orbits, so you can use equations of circular motion

Explain Rutherford's Scattering Experiment (See Diagram on page 60)

1. A stream of alpha particles form a radioactive source was fired at a very thin gold foil. 2. When alpha particles form radioactive source strike a fluorescent screen, a tiny visible flash of light is produced. 3. Geiger and Marsden recorded these flashes and counted the number of alpha particles scattered at different angles.

Explain: Forced Vibrations

1. A system can be forced to vibrate (or oscillate) by a periodic external force 2. The frequency of this force is called the driving frequency.

(Equation +) Describe and explain the SHM equations for acceleration (for normal and max).

1. According to the definition of SHM, the acceleration, a is directly proportional to the displacement, x. The constant of proportionality is equal to -ω² 2. There's a minus sign in the equation because the acceleration is always in the opposite direction to the displacement. Acceleration: a = -ω²x (In Formula Booklet) Max Acceleration: a(max)= ω²A (A is amplitude) (Not in Formula Booklet - LEARN)

Describe and explain what a a light year is

1. All electromagnetic waves travel at the speed of light, c, in a vacuum (c = 3.00 x10⁸ ms⁻¹). the distance that electromagnetic wave travels through a vacuum in one year is called a light-year (ly). 2. 1 ly is equivalent to about 9.5 x 10¹⁵

Explain how Potential is Potential Energy per Unit Charge

1. All points in an electric field have an electric potential, V. This is equal to the work done bringing a unit positive charge from a point infinitely far way to that point in the electric field. This means that an infinity, the electric potential will be zero. 2. This means that at infinity the electric potential will be zero.

Explain what Internal energy is

1. All things (solids, liquids, gases) have energy contained within them. 2. The amount of energy contained in a system is called its internal energy - it is found by summing the kinetic and potential energies of all the particles within it.

Briefly state the 4 different kinds of nuclear radiation

1. Alpha 2. Beta-minus (Beta) 3. Beta-plus 4. Gamma

Explain how Alpha (α) emission occurs

1. Alpha emission only happens from the nuclei of very heavy atoms like uranium and radium 2. The nuclei of these atoms are too massive to be stable 3. When an alpha particle is emitted, the proton number decreases by two and the nucleon number decreases y four.

Explain which releases more energy - nuclear fission or nuclear fusion

1. Although the energy released per nucleon is generally lower in nuclear fusion than fission (see binding energy cards), the nuclei used in fusion have a lower mass, so a mole of the reactants in a fusion reaction weighs less than a mole of the reactants in a fission reaction. 2. Gram for gram, fusion can release more energy than fission

Explain the relationship between the force and velocity in circular motion

1. Although the force changes direction of the motion, the object's velocity remains perpendicular to the direction of the force. 2. The object never moves towards or away from the centre of the circle, so there is no motion in the direction of the force. 3. Hence, no work is done on the object and the object's kinetic energy (and therefore speed) remains constant

How can you predict radioactive decay?

1. Although you can't predict the decay of an individual nucleus if you take a very large number of nuclei, their overall behaviour shows a pattern. 2. Any sample of a particular isotope has the same rate of decay i.e. the same proportion of nuclei will decay in a given time.

What is special about an object with SHM? Give 2 examples

1. An object with simple harmonic motion (SHM) oscillates to and fro, either side of a midpoint 2. Pendulums and mass-spring systems (e.g. a mass hanging on a spring that's free to move up and down are two examples.

Give the symbol and relative charge for the following anti-quarks: 1. Anti-up 2. Anti-Down 3. Anti-Strange

1. Anti-up, U, -2/3 2. Anti-down, d, +1/3 3. Anti-strange, s, +1/3 (all letters have bars over top)

Explain what makes an electric field

1. Any object with charge has an electric field around it - the region were it can attract or repel other charges 2. Force fields are force fields (see notes on gravity etc.) where charged objects will experience a non-contact force

Show how to derive the formula C = 4πε₀R for the capacitance of a capacitor

1. As it is a charge sphere, you can assume all of its charge is at the centre and treat it like a point charge 2. Substitute V = Q/C into V = Q/4πε₀R → Q/C = Q/4πε₀R (where R = the radius of the sphere). 3. Cancel out the Q's: 1/C = 1/4πε₀R 4. Rearrange for C which gives: C = 4πε₀R (which is in farads).

Explain what happens in terms of the physics when a capacitor is charged in the circuit on page 43

1. As soon as the switch closes, current starts to flow. The electrons flow onto the plate connected to the negative terminal of the power supply, so a negative charge builds up. 2. This build-up of negative charge repels electrons off the plates connected to the positive terminal of the power supply, making that plate positive. These electrons are attracted to the positive terminal of the power supply. 3. An equal but opposite charge builds up on each plate, causing a potential difference between the plates. Remember that no charge can flow between the plates. Remember that no charge can flow between the plates because they're separated by an insulator (gap or dielectric) 4. Initially the current through the circuit is high. But as charge builds up on the plates, electrostatic repulsion makes it harder and harder for more electrons to be deposited. When the p.d. across the capacitor is equal to the p.d. across the power supply, the current falls to zero. The capacitor is fully charged.

Explain how neutron stars are formed

1. As the core of a massive star contracts, electrons get squashed onto the atomic nuclei combining with protons to form neutrons and neutrinos (hence the name 'neutron star'). 2. If a white dwarf's core is 1.4 to 3 times the mass of the Sin them this is as far as the star can contract. The core suddenly collapses to a neutron star, causing a supernova.

Explain how Newton's Law of Gravitation can be used to investigate the thickness of a planet's atmosphere

1. As well as predicting the motion of satellites, Newton's law of gravitation can also help to explain how thick a planet's atmosphere is 2. The planet's gravitational field exerts a force on everything around it, including the particles which make up its atmosphere .Otherwise,the particles would float off into space. 3. The more massive the planet is, the larger the force is further away from the planet's surface - so the more atmosphere particles it can stop escaping into space, leading to a thicker atmosphere.

Derive the formula for Escape Velcotiy

1. As you know energy (kinetic energy + gravitational potential energy) is zero: 1/2mv² + (-GMm/r) = 0 so 1/2mv² = GMmr 2. Canceling the m's gives: 1/2v² = GM/r (this shows the escape velocity is the same for all masses in the same gravitational field 3. Rearrange for velocity, v: v² = 2GM/r → v = √(2GM/r)

Give the history of the universe before 10⁻⁴³ to 10⁻⁴ seconds

1. At the start of this periods there is no distinction between different types of force, there is just one grand unified force. 2. Then the universe expands and cools, and the unified force splits into gravity, strong nuclear, weak nuclear and electromagnetic forces. Most cosmologists believe the universe went through a rapid period of expansion called inflation at about 10⁻³⁴ seconds. 3. The universe is a sea of quarks, antiquarks, leptons and photons. The quarks aren't bound up in particles like protons and neutrons, because there's too much energy around. 4. At some point, matter-antimatter symmetry gets broken, so slightly more matter is made than antimatter. (No one knows exactly how or why this happens, but most cosmologists like to put it as early as possible in the history of the universe).

Explain percentage wise how much dark energy and dark matter make up the universe. Deduce from this how much of the universe we actually know about.

1. Based on current observations, dark energy makes up around 70% of the universe. 2. As dark matter makes up another 25%, this means that only 5% of the universe is made up ordinary matter. Or to put it another way, we have very little idea what 95% of the universe is made up of.

Explain when Beta-minus (β⁻) decay happens

1. Beta-minus (β⁻) decay is the emission of an electron from the nucleus along with an antineutrino 2. β⁻ decay happens in isotopes that are 'neutron rich' (have many more neutrons than protons in their nucleus) 3. One of the neutrons in the nucleus decays into a proton and ejects a beta-minus particle (an electron) and an antineutrino. 4. When a beta-minus particle is emitted, the proton number increases by one and the nucleon number stays the same

Briefly state the 3 gas laws

1. Boyle's Law: pV = Constant 2. The Pressure Law: P/T = Constant 3. Charles's Law: V/T = Constant

Who provided explanations for Brownian Motion and what did they discover?

1. Brown couldn't explain this 2. Einstein showed up 10 years late and showed this proved evidence for the existence of atoms or molecules in the air (the kinetic model of matter). 3. The randomly moving air particles were hitting the smoke particles unevenly, causing this motion.

What methods can be used in order to find the sizes of atoms? Give the diameter of an atom, and the smallest nucleus. What does this show?

1. By probing atoms using scattering and diffraction methods, we know that the diameter of an atom is about 0.1 nm (1 x 10⁻¹⁰ m and the diameter of the smallest nucleus is a few fm (1 fm = 1 x 10⁻¹⁵ m - pronounced "femtometers") 2. This shows that nuclei are really really tiny compared to the size of the whole atom (think of a ferris wheel as the atom and a grain of rice in the centre being the nucleus)

Give 2 uses of CAT/CT scans

1. CAT scans produce more detailed images that regular X-rays, especially for soft tissue. 2. The data can also be manipulated to produce a 3D image.

Why are parsecs used?

1. Calculating d in metres, or in AU would give some huge numbers. 2. Astronomers have defined a unit of distance from the angle of parallax. This is called a parsec

Give 3 uses for tracers

1. Can show areas of damaged tissue in the heart by detecting areas of decreased blood flow. This can reveal coronary artery disease and damaged or dead heart muscle caused by heart attacks 2. They can identify active cancer tumours by showing metabolic activity in tissue. Cancer cells have a much higher metabolism than healthy cells because they're growing fast, so take up more tracer 3. Tracers can show blood flow and activity in the brain. This helps research and treat neurological conditions like Parkinson's Alzheimer's, epilepsy, depression etc.

What makes capacitors so useful in applications?

1. Capacitors are found in loads of electric devices. 2. They don't store much charge, so can't replace batteries but they can discharge quicker than batteries, which makes them very useful. 2. What's more, the amount of charge that can be stored and the rate at which it's released can be controlled by the capacitor chosen.

Explain how number of protons and neutrons affect the chemical properties and stability of an element

1. Changing the number of neutrons doesn't affect the atom's chemical properties 2. The number of neutrons affects the stability of the nucleus (see other cards). 3. Unstable nuclei may be radioactive

(Equation +) Derive and explain the Equation of State Explain what each symbol is and give units

1. Combining all the gas laws gives the equation p(v/T) = Constant 2. The constant then becomes nR, where R is called the molar gas constant. ts value is 8.31 Jmol⁻¹K⁻¹. Plugging this in gives the following equation: P(V/T) = nR or rearranged pV = nRT <== The equation of state of an ideal gas p is Pressure (Pa), V is volume (m³), T is temperature (K), n is amount of gas in moles

In relation to the graph on page 76 explain the binding energy involved in nuclear fission and fusion. Check the graph for more info

1. Combining small nuclei is called nuclear fusion - this increases the binding energy per nucleon dramatically, which means a lot of energy is released during nuclear fusion. 2. Fission is when large nuclei are split in two. The nucleon numbers of the two new nuclei are smaller than the original nuclear, which means there is an increase in the binding energy per nucleon. So, energy is also released during fission (but not as much energy per nucleon as in nuclear fusion).

State the components of a nuclear reactor. (See diagram on page 78)

1. Control Rods 2. Concrete Case 3. Fuel Rods 4. Moderator (water) 5. Pump 6. Cool Water 7. Steam (to turbines)

Explain the role of control rods in a nuclear reactor. (See diagram on page 78)

1. Control rods control the chain reaction by limiting the number of neutrons in the reactor. 2. They absorb neutrons so that the rate of fission is controlled. Control rods are made up of a material that absorbs neutrons (e.g. boron) and they can be inserted by varying amounts to control the reaction rate. 3. In an emergency, the reactor will be shut down automatically by the release of the control rods in the reactor which will stop the reaction as quickly as possible.

Explain the role of the coolant in a nuclear reactor. (See diagram on page 78)

1. Coolant is sent around the reactor to remove heat produced in the fission - often the coolant is the same water that is used in the reactor as a moderator. 2. The heat from the reactor can then be used to make steam for powering electricity-generating turbines.

Explain what WIMPs are and the evidence behind this as a theory for dark matter.

1. Dark matter is made from WIMPs (Weakly Interacting Massive Particle). 2. These are exotic particles that don't interact with electromagnetic force, but with gravity. 2. No particle like this has ever been detected though and so are currently purely theoretical.

Explain what MACHOs are and the evidence behind this as a theory for dark matter.

1. Dark matter is made up of MACHOs (Massive Compact Halo Objects) - objects made up of normal matter in a very dense form, that don't give off light and so are far to detect (e.g. black holes, brown dwarfs (stars not big enough for fusion to take place). 2. Astronomers have had limited success looking for these objects - but it's unlikely that MACHOS made of normal matter account for all the dark matter in the universe, as this would require more protons and neutrons to exist than is compatible with the current understanding of the Big Band

Explain how you would measure the discharge of a capacitor according to the diagram on page 43.

1. Disconnect the power supply from the circuit and reconnect the circuit and close the switch 2. Let the capacitor discharge whilst the data logger records potential difference and current over time. 3. When the current through the ammeter and the potential difference across the plates fall to zero, the capacitor is fully discharged.

Explain what electric field strength is, relating to the formula E = F/Q

1. E is a vector pointing in the direction that a positive charge would move 2. The units of E are newtons per coulomb (NC⁻¹) 3. Field strength depends out where you are in the field 4. A point charge - or any body which behaves as if all its charge is concentrated at the centre - has a radial field

Give the mass of a proton or neutron and compare this. Use this to explain what the mass of the atom is in relation to the number of nucelons.

1. Each proton or neutron has a mass of (approx) 1 atomic mass unit (1.661 x 10⁻²⁷ kg). 2. The mass of an electron compared to a nucleon is virtually nothing, so the number of nucleons is about the same size as the atom's mass (in atomic mass units).

(Equation + ) Derive the Equation relating speed, mass and radius of a satellite.

1. Earth feels a force due to the gravitational 'pull' of the Sun. The force is given by Newton's law of gravitation: (F = -(GMm)/r² 2. The earth has velocity v. Its linear speed is constant but its direction is not - so it's accelerating . The centripetal force (p.14) causing the acceleration is: F = mv²/r 3. The centripetal force on the Earth must be a result of the gravitational force due to the Sun, and so these forces must be equal: (mv²)/r = (GMm)/r² which results in : * v = √(GM/r) *

Give some of the key properties of electric fields

1. Electric charge, Q, is measured in coulombs (c) and can be either positive or negative 2. Oppositely charged particles attract each other. Like charges repel 3. If a charged object is placed in an electric field, then it will experience a force 4. If a charged object is a sphere, and the charge is evenly distributed (it's spherically symmetrical), you can assume all of its charge is at its centre. 5. Just like with gravitational fields, electric fields can be represented by field lines.

Explain what electric potential energy is and how you can calculate it

1. Electric potential is the electric potential energy that a unit positive charge (+1 C) would have at a certain point. 2. This means you can find the electric potential energy for any charge at that point in the electric field by multiplying the electric potential by the value of the charge.

Give 2 examples of leptons and symbols and charge relative to e

1. Electrons (e⁻) charge = -1 2. Neutrino (ν) charge = 0

Explain how electrons exist in discrete energy levels in Atoms See diagram on Page 33

1. Electrons in an atom can only exist in certain well-defined energy levels. Each level is given a number, with n=1 representing the ground state 2. Electrons can move down an energy level emitting a photon 3. Since these transitions are between definite energy levels, the energy of each photon emitted can only take a certain allowed value. 4. The diagram on page 33 shows the energy levels for atomic hydrogen (the energies are all negative because of how 'zero energy' is defined).

(Equation +) Using pV=NkT and the pressure of an ideal gas given by kinetic theory: pV = 1/3Nmc² (with bar above c²) derive a formula relating Energy, boltzmann constant and temperature

1. Equate the two equations: 1/3Nmc² = NkT 2. Cancel out N's: 1/3mc² = kT 3. Rearrange (x3): mc² = 3kT 4. 1/2mc² is the average kinetic energy of an individual particle (based around 1/2mv²) so to get this, Multiply both sides by 1/2: 1/2mc² = 3/2kT So: E = 3/2kT

Explain the key relationship between particles and antiparticles

1. Every particle type has a corresponding antiparticle with the same mass but with opposite charge e.g. an antiproton is negatively charged particle with the same mass as the proton. (The masses are given in the exam for Protons Neutrons and Electrons, use your initiative) 2. This includes the neutrino which has an antiparticle called an antineutrino (although doesn't do much either)

Explain Dark Energy and how the theories of universe expanding/contracting have changed due to this.

1. Everything in the universe is attracted to everything else by gravity. This means the expansion of the universe should be slowing down 2. Historically, astronomers debating whether this would slow the expansion of the universe enough to cause it to contract back on itself (in a so called 'Big Crunch') 3. However in the late 1990s, astronomers discovered that actually the expansion of the universe appears to be accelerating rather than slowing down. Astronomers are trying to explain this acceleration using dark energy - a type of energy that fills the whole of space. 4. There are various theories of what this dark energy is, but it's really hard to test them. So like dark matter, it's currently a mystery.

How were quarks discovered?

1. Evidence for quarks came form hitting protons with high energy electrons 2. The way the electrons scattered showed hat there were three concentrations of charge (quarks) inside the proton

Explain the elements of the formula: g = F/m

1. F is the force experienced by a mass m when it's placed in the gravitational field . Divide F by m and you get the force per unit mass. 2. g is a vector quantity, always pointing towards the centre of the mass whose field you're describing. Depending on the direction defined to be positive, it could be negative 3. Since the gravitational field is almost uniform at the Earth's surface, you can assume g is a constant if you don't go too high. 4. g is just the acceleration of a mass in gravitational field - often called the acceleration due to gravity.

(Equation +) State and explain a formula for Field strength caused by two parallel plates. GIve unis

1. Field strength, E is the same at all pints between the two plates and is given by: E = V/d Where V is the potential difference between the plates and d is the distance between them 2. E can also be measured in volts per metre (Vm⁻¹)

Explain what happens with fission for Uranium-235 (See diagram on page 78 ensure you are happy with that) What is special about the neutrons used?

1. Fission can be induced by making a neutron enter a ²³⁵U nucleus, causing it to become very unstable. 2. This creates ⁹²₃₆Kr, ¹⁴¹₅₆Ba 3 neutrons (¹₀n) and energy. 3. Only low energy neutrons can be captures in this way. A low energy neutron is called a thermal neutron

Briefly state 3 uses of capacitors:

1. Flash Photography 2. Back-up power supplies 3. Smoothing out p.d.

Explain the Thomson Model

1. Following the discovery of the electron in the late 19th century, J.J Thomson proposed the Thomson model of the atom, know as the ;plum pudding' model. 2. This model said that atoms were made up of a globule of positive charge, with negative charged electrons sprinkled in it, like fruit in a plum pudding. 3. It was widely accepted at the time, til the Rutherford Scattering experiment of 1909. This was where Hand Geiger and Ernest Marsden studied the scattering of alpha particles by thin metal foils.

Explain what the electric field lines look like, and the reaction when a test charge is brought near a positive and negative charge. (See pics on page 46)

1. For a positive, Q, the small positive 'test' charge q would be repelled, so the field lines point away from Q 2. For a negative Q, the small positive charge q would be attracted, so the field lines point towards Q (Electric field lines always go from + to -)

Give some key points to do with the graph on page 76 with Binding Energy per Nucleon v. Nucleon Number

1. For all elements, the line of best fit shows a curve. A high binding energy per nucleon means that more energy is needed to remove nucleons from the nucleus 2. In other words the most stable nuclei occur around the maximum point on the graph - which is at nucleon number 56 (Iron, Fe, the most stable element).

What is special about the graph of Temperature v. Pressure when it comes to the pressure law?

1. For any ideal gas, the line meets the temperature axis at -273°C - that is absolute zero 2. If the graph is in kelvins, it would go through the origin.

Explain what Astronomical Units are (AU) State the conversion between AU and km

1. From Copernicus onwards, astronomers were able to work out the distance the planets are form the sun relative to the Earth, using astronomical units (AU) but they could not work out the actual distances. 2. The size of the AU was measured accurately in 1769 during a transit of Venus (when Venus passed between the Earth and the Sun). 3. We know that 1 AU = 150 million km

Describe and explain the terms cycle, frequency, period in terms of SHM

1. From maximum positive displacement (e.g. maximum displacement to the right) to maximum negative displacement (e.g. to the left) and back again is called a cycle of osccilaltion 2. The frequency, f, of the SHM is the number of cycles per second (measured in Hz). 3. The period, T, is the time taken for a complete cycle (in seconds)

What are leptons?

1. Fundamental particles and they don't feel strong nuclear force 2. They interact with other particles via weak nuclear force and gravity (and electromagnetic force if they're charged).

For Gamma radiation give the following information: 1. It's symbol 2. The Constituent 3. Relative Charge 4. Mass (u - atomic mass unit)

1. Gamma 2. γ 3. Short-wavelength high-frequency electromagnetic wave 4. 0 5. 0

Explain how Gamma (γ) radiation is emitted

1. Gamma (γ) rays can be emitted from a nucleus with excess energy - we say that the nucleus is excited. 2. The energy is lost by emitting a gamma ray 3. This often happens after an alpha or beta decay has occurred

Where are gamma camres useful? Evaluate the advantages and disadvantages

1. Gamma cameras are useful in helping to diagnose patients without the need for surgery 2. They are also cheaper than a PET scanner but still fairly expensive 3. They also use ionising radiation which is bad for you (see other cards).

What is an ideal gas? How do real gases behave in comparison?

1. Gases that obey all the assumptions of the kinetic model are called ideal gases. 2. Real gases behave like ideal gases as long as the pressure isn't too big and the temperature is reasonably high (compared to their boiling points).

Explain what Geostationary Satellites are.

1. Geostationary satellites orbit directly over the equator and are always above the same point on Earth 2. A geostationary satellite travels at the same angular speed as the earth turns below it 3. Their orbit takes exactly one day

Name the 4 big similarities between Electric Fields and Gravitational Fields

1. Gravitational field strength, f, is force per unit mass, Electric field strength, E, is the force per unit positive charge. 2. Newton's law of gravitation or the force between two point masses is an inverse square law, and Coulomb's law for the electric force between two point charges is also an inverse square law. 3. See diagrams comparing the field lines for a spherical mass and the field lines for a negative spherically symmetric charge. (page 49). 4. Gravitational potential, V, is potential energy per unit mass and is zero at infinity, and Electric potential, V is potential energy per unit positive charge and is zero at infinity.

State the 3 differences between gravitational and electric fields

1. Gravitational forces are always attractive. Electric forces can be either attractive or repulsive. 2. Objects can be shielded from electric fields, but not from gravitational fields 3. The size of an electric force depends on the medium between the charges, e.g. plastic or air. For gravitational forces, this makes no difference.

Explain why the gravitational potential is negative and what the formula V(g) = -GM/r shows

1. Gravitational potential is negative - you have to do work against the gravitational field to move an object out of it. 2. The further you are from the centre of a radial field, the smaller the magnitude of V(g).. 3. At an infinite distance from the mass, the gravitational potential will be 0.

How would you estimate the Specific Heat Capacity of a Metal Block using the Method of Mixtures? (Some b's, s's and w's are subscript. See page 6 for clarification)

1. Heat a block of known mass mw up to a temperature Tb 2. Quickly transfer this block into a container containing a mass of water, mw, at a temperature Tw. 3. The hot block will heat the water. Measure the temperature of water once it has reached a steady value, Ts. 4. The heat (energy) gained by the water is equal to the heat lost by the block so: mwcwΔθw = mbcbΔθb which becomes mwcw(Ts-Tw) = mbcb(Tb-Ts) 5. Rearrange for Cb this makes: cb = (mwcw(Ts-Tw))/(mbcb(Tb-Ts))

How would you conduct an experiment and find the specific heat capacity of the material? (2/2)

1. Heat the substance with the heater. You need a temperature rise of about 10 K to get an accurate value of C. 2. With an ammeter and voltmeter attached to your electric heater you can work out the energy supplied 3. Plug data into E = mcΔθ to calculate c (Alternatively you can plot a graph - practical book for more detail).

Explain the process of Nuclear Fission Explain what happens to energy during this process

1. Heavy nuclei (e.g. uranium) are unstable. Some can randomly split into two smaller nuclei (and sometimes several neutrons) - this is called nuclear fission. 2. Energy is released during nuclear fission because the new, smaller nuclei have a higher binding energy per nucleon (see page 76-77) and a lower total mass.

What affects how much energy is absorbed in X-ray scans? How is this useful?

1. How much energy is absorbed by a material depends on its atomic number. 2. Tissues containing atoms with different atomic numbers (e.g. soft tissue and bone) will contrast on the X-ray image

Explain Quark Confinement

1. If a proton was blasted with enough energy, would you separate out the quarks? No. 2. The energy just gets changed into more quarks and antiquarks - it's pair production again and it makes mesons. This is called quark confinement (See diagram on page 68)

Explain what Rutherford's Scattering Experiment should have shown if the thomson model was right, and what they actually saw

1. If the Thomson model was right, all the flashes should have been seen within a small angle of the beam. This wasn't what they saw. 2. Geiger and Marsden observed that most alpha particles went straight through the foil, but a few scattered at angles greater than 90°, sending them back to where they came.

What happens in a nuclear reactor, if the reaction is let unchecked? Give an example of where could be intentionally used

1. If the chain reaction in a nuclear reactor is let to continue unchecked, large amounts of energy are released in a very short time 2. Many new fissions will follow each fission, causing a runaway reaction which could lead to an explosion. This is what happens in a fission (atomic) bomb.

Explain how using Coulomb's Law you can get positive and negative values for F (See Diagram on page 46)

1. If the charges are opposite, then the force is attractive, F will be negative 2. If Q and q are like charges then the force is repulsive and F will be positive

Explain how black holes are formed + give their properties.

1. If the core of a star is more than 3 times the Sun's mass, the neutrons can't withstand the gravitational forces and the star continues to collapse. 2. For something of this size, there are no known mechanisms left to stop the core collapsing to an infinitely dense point called a singularity. At that point, the laws of physics break down completely. 3. Up to a certain distance away the gravitational pull is so strong that nothing, not even light, can escape it - it's called a black hole. The boundary of this region is called the event horizon.

Explain what to do in gas law experiments if markings are quite far apart

1. If the markings on your measuring equipment are quite far apart you can usually interpolate between them . 2. (e..g. if the temperature is halfway between the markings for 24°C and 25°C you could record it as 24.5°C 3. However it's better to use something with a finer scale if you can

Explain how to calculate the age of the observable universe

1. If the universe has been expanding at the same rate for its whole life, the age of hte universe is: t = H₀⁻¹ 2. Unfortunately, since no one knows the exact value o H we can only guess the universe's age. This is 14 billion years (see textbook for calculation and conversions).

What can be done if if tissues in a reigion of interests have similar attenuation coefficients when performing an X-ray?

1. If tissues in the region of interest have similar attenuation coefficients then artificial contrast media can be used e.g. barium meal or idone. 2. These have high atomic numbers, so they show up clearly in X-ray images and can be followed as they move through a patients body.

(Equation +) Derive and explain an equation relating pressure, volume, Number of Particles, Boltzmann constant, and temperature.

1. If you combine N = n x NA and k = R/NA, you'll see that Nk = nR. 2. This can be substituted into the equation of state to give this alternative form (in terms of the number of particles N, rather than the moles, n) pV = nkT p = Pressure (Pa) V = volume (m³) T = temperature (K) N = number of particles k = Boltzmann constant (1.30x10⁻²³)

Explain how Hot Gasses produce Line Emission Spectra (Page 34)

1. If you heat a gas to a high temperature, many of its electrons move to higher energy levels 2. As they all back down to the ground state, these electrons emit energy as photons 3. Splitting the light from a hot gas sing a diffraction grating gives you a line spectrum 4. Each line on the spectrum corresponds to a particular wavelength of light emitted by the source. Since only certain photon energies are allowed, you can only see the corresponding wavelengths. You can calculate the wavelength, λ, of each line in a line emission spectrum using dsinθ = nλ (where d is the slit spacing of the grating and θ is the angle from the zero order lie), if you know which order maxima the spectrum is. 5. Different atoms have different energy levels and so different sets of emission spectra. This means you can identify a gas from its emission spectrum.

Explain how you can determine the work done using the graph on page 48

1. If you move a unit charge and change its electric potential, you have to apply a force and do work. 2. For a point charge (and therefore for a spherical charge (see other cards) you can ploy the force applied (F)against the distance (r), form the charge producing the electric field. 3. THis is an inverse square law (see other cards on this) and the area under the graph gives the work done.

Explain the gravitational field lines of the earth in relation to a small mass m (See diagram on page 22)

1. If you put a small mass, m, anywhere in the Earth's gravitational field, it will always be attracted towards the earth 2. The Earth's gravitational field is radial - the lines of force meet at the centre of the Earth. 3. If you move mass m further away from the Earth - where the lines of force are further apart - the force it experiences decreases. 4. The small mass, m, has a gravitational field of its own. This doesn't have a noticeable effect on the Earth though because the Earth is so much more massive. 5. Close to the Earth's surface, the field is (almost) uniform - the field lines are (almost) parallel and equally spaced. You can usually assume that the field is perfectly uniform.

Describe and explain what happens when two or more capacitors are placed in parallel.

1. If you put two or more capacitors in a parallel circuit the potential difference across each one is the same. 2. Each capacitor can store the same amount of charge as it would if it was the only component in the circuit 3. Therefore the total capacitance is just the sum of the individual capacitances Ctotal = C₁ + C₂ ...

Explain how light years can be used to work out the size of universe (briefly).

1. If you see light from a star that is, say, 10 light-years away then you're actually seeing it as it was 10 years ago. The further away the object is, the further back in time you are actually seeing it. 2. The further away the object is, the further back in time you are actually seeing it. So when we look at stars we are looking back in time, and we can only see as far back as the beginning of the universe. This means we can work out the size of the observable universe.

Explain how a diffraction grating can be used to find the wavelength of light (Look at the diagram on page 33)

1. If you shine monochromatic light (light with a single wavelength or frequency) through a diffraction grating, you get a pattern of bright lines (maxima) on a dark background. This is a result of the light interfering with itself constructively and destructively (like at AS). 2. Line of maximum brightness at the centre is called the zero order line, the next lines on each sides are called the first order lines and so on 3. Using the fringe width (the distance between the maxima), x, and the distance to the screen, D, the angel the first order line makes with the zero order line can be calculated using the small angle approximation - that θ = tanθ = x/D

Explain: Free Vibrations

1. If you stretch and release a mass on a spring it oscillates at its natural frequency 2. If no energy is transferred to or from the surroundings, it will keep oscillating with the same amplitude forever 3. In practice this never happens, but a spring vibrating in the air is called a free vibration (or oscillation) anyway.

Explain the Doppler Effect

1. Imagine an ambulance driving past you.. As it moves towards you, its siren sounds higher-pitched but as it moves away, its pitch is slower. The change in frequency and wavelength is called the Doppler shift. 2. The frequency and wavelength change because the waves bunch together in front of the source and stretch out behind it. THe amount of stretching or bunching together depends on the velocity of the source.

Explain what Parallax is

1. Imagine you are in a moving car. You see that stationary objects on the foreground seem to be moving faster than objects in the distance. This apparent motion is called parallax. Parallax is measured in terms of the angle of parallax. 2. The same thing happens as the Earth orbits the Sun. At different points in the Earth's orbit, nearby stars appear to move relative to very distance stars. 3. By measuring the angle that a nearby star seems to move through as the Earth moves round its orbit, you can work out how far away the star is.

Describe and explain an experiment to estimate absolute zero (Pressure Law) (See Page 8 for diagram)

1. Imerese a stoppered flask of air in a beaker of water so that as much as possible of the flask is submerged. Connect the stopper to a Bourdon gauge using a short length of tube - the volume of the tubing must be much smaller than the volume of the flask. Record the temperature of the water and the pressure on the gauge. 2. Heat the water for a few minutes then remove the heat, stir the water to ensure it is at a uniform temperature and allow some time for the heat to be transferred from the water to the air. Record the pressure on the gauge and the temperature, then heat the water again and repeat until the water boils. 3. Repeat your experiment twice more with fresh cool water 4. Plot you results on a graph of pressure against temperature (in °C). Draw a line of best fit. Estimate the value of absolute zero by continuing (extrapolating) your line of best fit until it crosses the x axis (should hit -273°C).

Explain the idea of Brownian Motion

1. In 1827, botanist Robert Brown noticed that tiny particles of pollen suspended in water moved with a a zigzag, random motion. 2. This type of movement is known as Brownian motion

Describe and explain (with a specific example) the risks of accidents and natural disasters to nuclear power plants. What is the effect of this?

1. In 2011, an earthquake and subsequent tsunami in Japan caused a meltdown at the Fukushima power plant. Over 100 000 people were evacuated from the area, and many tonnes of contaminated water leaked into the sea. 2. THe perceived risk of this kind of disaster leads many people to oppose the construction of nuclear power plants near their homes

Explain how PET scans work

1. In a PET (positron emission tomography) scan, the patient is injected with a substance used by the body, e.g. glucose, containing a positron-emitting radiotracer with a short half-life e.g. ¹³N ¹⁵O ¹⁸F. 2. The patient is left for a time to allow the radiotracer to move through the body to the organ 3. Positron emitted by the radioisotope collide with the electrons in the organs, causing them to annihilate, emitting high-energy gamma rays in the process. 4. Detectors around the body record these gamma rays, and a computer builds up a map of the radioactivity in the body

(Equation +) Describe the relationship between E and r² in a Radial Field

1. In a Radial Field, E is Inversely Proportional to r² 2. When the electric field is being generated by a point charge, we call the charge generating the field Q and redefine the charge experiencing the force as q. In a radial field, E depends on the distance r form the point charge Q. E = Q/(4πε₀r²) 3. It's another inverse square law: E ∝ 1/r² (the area under the graph is the electric potential) 4. Electric field strength increases as you go further away from Q - on a diagram the field lines get further apart.

Explain what an B-Scan is (See diagram on page 85)

1. In a brightness scan (B-Scan) the electron beam sweeps down the screen rather than across 2. The amplitude o the reflected pulses is displayed as the brightness of the spot 3. You can use a linear array of transducers to produce a two-dimensional image.

Explain what a uniform field is and how it can be produced

1. In a uniform field, field strength is the same everywhere. 2. A uniform field can be produced by connecting two parallel plates to the opposite poles of a battery

Explain when Beta-plus (β⁺) decay happens

1. In beta-plus emission, a proton gets changed into a neutron releasing a positron and a neutrino. 2. The proton number decreases by one, and the nucleon number stays the same

Explain what happens after Red Giant stars for low/medium mass stars (like the Sun).

1. In low-mass stars, the carbon-oxygen core isn't hot enough for any further fusion and so it continues to contract under its own weight. Once the core has shrunk to about Earth-size, electrons exert enough pressure (electron degeneracy pressure) to stop it collapsing any more. 2. This only works for stars with a core mass under 1.4 times the mass of the sun though - in bigger stars the electron degeneracy pressure isn't enough to counteract the gravitational force and the star collapses (see other cards for more). The maximum mass for which the electron degeneracy pressure can counteract the gravitational force is called the Chandrasekhar limit. 3. For stars below the Chandrasekhar limit, the helium shell becomes increasingly unstable as the core contracts. The star pulsates and ejects its outer layers into space as a planetary nebula, leaving behind the dense core. 4. The star is now a very hot dense solid called a White Dwarf which will simply cool down and fade away.

Explain Damping

1. In practice, any oscillating system loses energy to its surroundings. 2. This is usually down to the frictional forces like air resistance 3. These are called damping forces 4. Systems are often deliberately damped to stop them oscillating or to minimise the effect of resonance. 5. Damping reduces the amplitude of the oscillation over time. The heavier the damping, the quicker the amplitude is reduced to zero

Explain how half life can be calculated, and what this shows

1. In practice, half-life isn't measured by counting nuclei but by measuring the time it takes the activity or count rate to halve 2. The longer the half-life of an isotope, the longer it stays radioactive 3. You can't tell when any one nucleus is going to decay, but you can predict how many nuclei will decay in a given time period by generating a graph of N v t.

Explain the history of dark matter and how it was descovered

1. In the 1930s, Astronomer Fritz Zwicky calculate the mass of a cluster of galaxies (the COMA cluster) based on the velocity of its outer galaxies and compared this figure to the mass of the cluster as estimated form its luminosity. The mass calculated from the velocity was much bigger, suggesting there was 'extra' mass in the cluster that couldn't be seen. 2. In the 1970s, Vera Rubin observed that stars at the edges of galaxies were moving faster than they should given the mass and distribution of stars in the galaxy. For Newton's laws to hold, there needed to be extra matter in the galaxies that hadn't been accounted for. 3. These observations suggest there is something extra in the universe, giving mass to galaxies that we can't see. 4. This theoretical substance has been called 'dark matter'.

Describe and explain 2 ways to increase the beam intensity of an x-ray beam

1. Increase the tube voltage. This gives the electrons more kinetic energy. Higher energy means electrons can knock out electrons from shells deeper within the tungsten atoms 2. Increase the current supplied to the filament. As the current increases, the filament temperature rises. This liberates more electrons per second (with the same final energy per electron as before), which then produce more X-ray photons per second.

Explain how the Nuclear Model explained Rutherford Scattering (See pic on page 60)

1. Inside every atom, there's a positive nucleus containing neutrons (which have no charge) and positively charged protons. Protons and neutrons are known as nucleons. Orbiting this core are the negatively charged electrons 2. The charge on an electron -e is equal and opposite to the charge on a proton, +e. e is the elementary charge 1.60 x 10⁻¹⁹ C. 3. The nucleus only makes up a tiny proportion of an atom - it is about one 10,000th of the size of the whole atom. The electrons orbit at relatively cast distances from the nucleus, therefore most of the atom is simply empty space. 3. The proton and neutron are roughly 2000 times more massive than the electron, so the nucleus makes p nearly all of the mass of the atom.

Explain how isotopes are named

1. Isotopes are often named using their nucleon number - e.g. carbon isotopes include carbon-12 and carbon 13. 2. Other isotopes have special names e.g. deuterium and tritium (1 naturally occurring isotopes of hydrogen).

(Equation +) Explain the equivalence of energy and mass Give the equation relating these things

1. It all comes from Einstein's special theory of relativity 2. Energy can turn into mass and mass can turn into energy if you know how. This gives the famous formula: ∆E = ∆mc²

Explain why Technetium-99m is used in commonly in medical tracers

1. It emits γ-radiation. 2. Has a half-life of 6 hours (long enough for data to be recorded, but short enough to limit the radiation to an acceptable level. 3. It decays to a much more stable isotope

Explain the Cosmology Principle

1. It is easy to imagine the Earth as the centre of the universe, or that there's something really special about it. Earth is special to us because we live here, but on a universal scale it is like any other lump of earth. 2. The demotion of Earth from anything special is taken to its logical conclusion with the Cosmology principle. 3. This is the powerful idea - it means we can apply what we know about physics on the Earth and in our Solar System to the rest of the universe.

Explain where the Sun is as part of Stellar Evolution Explain the past and future

1. It is just like any other low mass star - starting off as a cloud of dust and gas and evolved to be a main sequence star that we see today. 2. This will most likely mean it will become a red giant and then finally a white dwarf.

Explain what the Root Mean Squared Speed is (or crms) (rms subscript)

1. It often helps to think about the motion of a typical particle in kinetic theory 2. c(bar)² is the mean square speed and has units m²s⁻² 3. c(bar)² is the average of the squared speeds of all the particles, so the square root of it gives you the typical speed. 4. This is called the root mean square speed, or usually the r.m.s speed. It is often written as crms. The unit is the same as any speed - ms⁻¹ 5. Crms can be found by square rooting the mean square speed √(c²)

Explain the calculations with annihilation

1. Just like with pair production, you can calculate the minimum energy of each photon produced (i.e. assuming that the particles have negligible kinetic energy). 2. The combined energy of the photons will be equal to the combined energy of the particles, so 2Eᵧ = 2mc² and so Eᵧ = mc² 3. You can also calculate the minimum frequency and maximum wavelength as before

(Extra?) Explain the origin of Kepler's Laws

1. Kepler came up with three laws about 1600, about 80 years before Newton developed his law of gravitation. 2. They're usually used to describe the planets in our solar system, but they can be used for any object and its satellite.

Give the 5 main pats of a gamma camera (see picture on page 82)

1. Lead shield - stops radiation from other sources entering the camera 2. Lead collimator - a piece of lead with thousands of vertical holes in it - only γ-rays parallel to the holes can pass through. 3. Sodium iodide crystal - emits a flash of light (scintillates) whenever a γ-ray hits it 4. Photomultiplier tubes - detect the flashes of light from the crystal and turn them into pulses of electricity 5. Electronic circuit - collects the signals from the photomultiplier tubes and sends them to a computer for processing into an an image which is used to help the doctor diagnose the patient.

Explain the properties and difference between lightly damped and heavily damped systems

1. Lightly damped systems have a very sharp resonance peak. Their amplitude only increases dramatically when the driving frequency is very close to the natural frequency 2. Heavily damped systems have a flatter response. Their amplitude does not increase very much near the natural frequency and they aren't as sensitive to the driving frequency.

Explain what H-R DIagrams are used for (Luminosity v. Temperature)

1. Luminosity is a measure of how bright an object is. IF you plot luminosity against temperature for stars, stars appear to group in distinct areas on the plot 2. The distinct areas show the main stages of the star life cycle: the main sequence, red giants, super red giants and white dwarfs. This is called a Hertzsprung-Russell diagram

Briefly state 3 possible explanations for what dark matter is

1. MACHOs 2. WIMPS 3. Doesn;t really exist

Explain the safety measures you will take in an experiment to investigate circular motion. (3/3 of experiment) (Some W's are subscript - see page 15 for clarity)

1. Make sure that the bung and the washers are securely fastened to the string. 2. Ensure you're not standing too close to anyone and there's nothing breakable nearby. 3. Of course safety goggles are also a good plan.

Give the symbol and power relative to a farad of: 1. Microfarads 2. Nanofarads 3. Picofarads

1. Microfarads - μF - x10⁻⁶ 2. Nanofarads - nF - x10⁻⁹ 3. Picofarads - pF - x10⁻¹² (Farads are pretty huge units)

Give the important conclusions from the Rutherford experiments

1. Most of the fast, charged alpha particles went straight through the oil. So the atom is mainly empty space 2. Some of the alpha particles were deflected through large angles, so the centre of the atom must have a large, positive charge to repel the, Rutherford named this the nucleus. 3. Very few particles were deflected by angles greater than 90 degrees, so the nucleus must be tiny. 4. Most of the mass must be in the nucleus, since the fast alpha particles (with high momentum) are deflected by the nucleus. So most of the mass and the positive charge in a atom must be contained within a tiny, central nucleus.

Give the properties of neutron stars

1. Neutron stars are incredible dence (about 4 x 10¹⁷ kgm⁻³). They're also very small, typically about 20 km across, and they can rotate very fast (up to 600 times a second). 2. They emit radio waves in two beams as they rotate. These beams sometimes sweep past the earth and can be observed as radio pulses rather like the flashes of a lighthouse. These rotating neutron stars are called Pulsars.

Do all hadrons have 3 quarks? Explain why, be sure to mention what mesons are

1. Not all hadrons have 3 quarks though. Protons and neutrons are a type of hadron called baryons which are made up of three quarks. 2. There are also hadrons made up of a quark and an anti-quark called mesons but we don't need to know about them

Explain what hadrons are and what they are made up of

1. Not all particles can feel the strong nuclear force, the ones that can are called hadrons. 2. They aren't fundamental particles. They're made up of smaller particles called quarks. know about these.

What is special about nuclear density, and its relationship with atomic density. From this, give 3 facts about the atom

1. Nuclear density is pretty much the same, regardless of the element - roughly 10¹⁷ kgm⁻³ 2. Nuclear density is much higher than atomic tensity. This suggests that: A. Most of the atom's mass is in its nucleus B. The nucleus is small compared to the atom C. An atom must contain a lot of empty space

Give 2 advantages for using nuclear plants.

1. Nuclear fission does not produce carbon dioxide, unlike burning fossil fuels, so it does not contribute to global warming 2. It also provide a continuous energy supply, unlike many renewable source (e.g. wind/solar).

Explain how a nuclear reactor works in terms of the science behind it, and the source of the fuel. (See diagram on page 78)

1. Nuclear reactors use rods of uranium that are rich in ²³⁵U as 'fuel' for fission reactions. (The rods also contain a lot of ²³⁸U, but that doesn't undergo fission). 2. These fission reactions produce more neutrons which then induce other nuclei to fission - this is called a chain reaction 3. The neutrons will only cause a chain reaction if they are slowed down, which allows them to be captured by the uranium nuclei - those slowed down neutrons are called thermal neutrons.

Explain the conditions needed for nuclear fusion

1. Nuclei can only fuse if they have enough energy to overcome the electrostatic (Coulomb) repulsion between them (see notes on electric field) and get close enough for the strong interaction to bind them 2. This means fusion reactions require much higher temperatures than fission as well as high pressures (or high densities). Under such conditions, generally only found inside stars, matter turns into a state called plasma.

Explain what the peak wavelength of a star is See important graph on page 35 (max) is in subscript

1. Objects emit electromagnetic radiation due to their temperature - at everyday temperatures this is mostly in the infrared part of the spectrum (which we can't see). But heat something up enough and it will start to glow 2. Stars can be assumed to emit radiation in a continuous spectrum 3. The relationship between intensity ('power per unit area') and wavelength for this radiation varies with temperature, as shown in the graph on page 35 4. The most common wavelength becomes shorter as the surface temperature of the star increases. This called the peak wavelength, λ(max)

Explain moles and Avogadro's Constant, and give it's value.

1. One mole of any material contains the same number of particles, no matter what the material is. 2. This number is called Avogadro's Constant and has the symbol NA (A is subscript) 3. The value of NA is 6.02x10²³ particles per mole

How efficient is the X-ray tube? Explain the issue caused by the heat, and how this is solved

1. Only about 1% of the electron's kinetic energy is converted into X-ray. The rest is converted into heat. 2. So, to avoid overheating, the tungsten anode is rotated at about 3000rpm. It's also mounted on copper - which conducts the heat away effectively.

Give some examples of resonance

1. Organ pipe: the column of air resonates driven by the motion of air at the bass 2. Swing: A swing resonates if it's driven by someone pushing it its natural frequency 3. Glass smashing: A glass resonates when driven by a sound wave of the right frequency. This can make the glass break 4. Radio: A radio is tuned so the electric circuit resonates at the same frequency as the radio station you want to listen to.

Explain the Piezo Effect and how ultrasound images are produced by it (see diagram on page 84)

1. Piezoelectric crystals produce a potential difference when they are deformed (squashed or stretched) - the rearrangement in structure displaces the centres of symmetry and their electric charges 2. When you apply a p.d. across a piezoelectric crystal, the crystal deforms. If the p.d. is alternating then the crystal vibrates at the same frequency. 3. A piezoelectric crystal can act as a receiver of ultrasound converting sound waves into alternating voltages, and also as a transmitter, converting alternating voltages into sound waves. 4. Ultrasound transducers use lead zincornate titanate (PZT) crystals. The thickness of the crystal is half the wavelength of the ultrasound that it produces. Ultrasound of this frequency will make the crystal resonate (see other cards on resonance) and produce a large signal 5. The PZT crystal is heavily damped to produce short pules and increases the resolution of the device

(Equation +) State and explain the formula relating the gravitational field strength with radius, Mass and the Gravitational constant See graph on page 23

1. Point masses have radial gravitational fields (see other cards). 2. The value of g depends on the distance r from the point mass M. This gives: g = -GM/r² It is another example of an inverse square law - as r increases, g decreases.

Explain the two graphs on page 48

1. Positive charge Q: V is initially positive and tends to zero as r increases towards infinity. 2. Negative charge Q: V is initially negative and tends to zero as r increases towards infinity.

Explain the idea that dark matter doesn't exist at all and the evidence behind this.

1. Probability that dark matter doesn't really exist at all - it is an illusion created by mistakes in other theories 2. Most scientists agree that it is there, even f we don't know what it is yet.

Explain how protactinium-234 is formed and what a protactinium generator is.

1. Protactinium-234 is formed when uranium decays (via another isotope. 2. You can measure protactinium-234's decay rate using a protactinium generator - a bottle containing a uranium salt, the decay products of uranium (including protactinium-234) and two solvents which separated out into layers (see pic on page 74).

Give the quark composition of a proton and neutron and anti-proton and neutron

1. Proton - uud (their total relative charges add to 1) (akak udu) 2. Neutron (their total relative charges add up to 0) Remember 'dud' as they have no charge Antiprotons and neutrons are the same just with the relative anti-quark - eg. same letter but with lines above them.

Give examples of hadrons

1. Protons and neutrons are hadrons. This is why they can make atomic nuclei - the nucleus of an atom is made up from protons and neutrons held together by the strong nuclear force. 2. As well as protons and neutrons, there are other hadrons that you don't get in normal matter like sigmas (∑) and mesons - although we don't need to know these

(Equation) Give the formulas for charge + voltage of a charging capacitor. Explain symbols and give units

1. Q = Q₀(1 - e^(-t/CR)) 2. V = V₀(1 - e^(-t/CR)) Where Q₀/V₀ is the voltage/current of the capacitor when it's fully charged (C) t is the time since discharging began (s) R is the resistance (Ω) C is the capacitance (F)

What are medical tracers? What is the key advantage of them over standard X-ray imaging?

1. Radioactive substances that are used to show tissue or organ function. 2. Other types of imaging e.g. X-rays only show the structure of organs - medical tracers show the structure and function.

Explain how you can use a graph (of N v t) to ind the half-life of an isotope

1. Read off the number of undecayed nuclei when t = 0 2. Go to half the original value of N, and draw a horizontal line to the curve, then a vertical line down to the x axis. 3. The half life is where this line meets the x axis 4. To check answer: repeat steps 1-3 for a quarter of the original value of N, and divide the time where the line meets the x axis by two. You can do the same for an 8th of the original value (divide time by 3) and a sixteenth. Check you get the same answer either way.

(Equation +) Explain acoustic impedance. (Equation) Give the equation of the wave intensity that is reflected. Brackets = subscript characters

1. Say an ultrasound wave travels through a material with an impedance Z₁. It hits the boundary between this material and another with an impedance Z₂. This incident wave has an intensity of I₀. 2. If the two materials have a large difference in impedance, then most of the energy is reflected (the intensity of he reflected wave I(r) will be high). If the impedance of the two materials is the same, then there is no reflection 3. This gives the equation I(r)/I₀ = (Z₂-Z₁)²/(Z₂+Z₁)²

Explain an experiment you can conduct to Investigate Capacitors in Series and Parallel

1. Set up a test series circuit to measure current and potential difference. Add a variable resistor and a switch. Close the switch. (See page 41 for diagram) 2. Constantly adjust the variable resistor to keep the changing current constant for as long as you can (it's impossible when the capacitor is nearly fully charged). 3. A data logger connected to the voltmeter can be used to record the potential difference over time. Once the capacitors are fully charged, open the switch. 4. Rearrange the circuit so the capacitors are in parallel. Make sure that they have been discharged first. Close the switch and repeat step 2 5. Once both circuits have been tested, you can plot graphs of current against time and charge against potential difference (using ∆Q = I∆t).

Explain how you would investigate Simple Harmonic Motion using data loggers etc. Make sure you mention how you can make your experiment repeatable

1. Set up the equipment as shown on the diagram on page 18 2. Lift the mass slightly and release it - this will cause the mass-spring system to start oscillating with simple harmonic motion. - Repeatability: Place a ruler behind the spring to measure how far you raise the mass, make sure you eye is level with the mass when you take the measurement and try to lift the mass straight p to stop the mass from swinging side to side. 3. As the mass oscillates, the position sensor will measure the displacement of the mass over time. (The computer can be set to measure this automatically. 4. Let the experiment run until you have got a good amount of data - say 10 oscillations + 5. Use data to draw displacement-time graph 6. Use the graph to measure, T, the time period of the oscillation and A, the amplitude of the oscillation.

Describe and Explain how to investigate Simple Harmonic Motion without a datalogger

1. Set up the experiment a shown on page 19. 2. Measure the weight of the mass and use a ruler to find the length of the string 3. Move the mass from side to side, keeping the string taught. Measure the angle between the string and the vertical reference line using the protractor. Make sure this is less than 10 degrees or the mas won't swing with SHM when you release it. 4. Release the mass. Position your eye level with the mark on the card, and start the stopwatch when the mass passes in front of it. 5. Record the time when the mass passes the mark again, moving in the same direction (this is the time period of the oscillator). To increase accuracy, measure say 5 to 10 complete oscillations and take an average. 6. You can investigate how different factors affect the motion of the pendulum by: changing the weight of the mass on the string, the length of the string, and the angle that you turn the string before you release it (as long as it is under 10 degrees). 7. You should find that the angle of the initial displacement and the weight of the mass have no effect on the time period of the pendulum, but as the length of the string increases, the time period increases.

Explain how you can investigate what happens when you charge a capacitor, using the circuit on page 43.

1. Set up the test circuit shown in the circuit diagram (on page 43). 2. Close the switch to connect the uncharged capacitor to the power supply 3. Let the capacitor charge whilst the data logger records both the potential difference (from the voltmeter) and the current from the ammeter) over time 4. When the current through the ammeter is zero the capacitor is fully charged 5. You can use a computer to plot a graph of charge, pd. or current against time. Remember to use ∆Q = I∆t

Explain how you can do an experiment to generate a count-rate decay graph, using protactinium-234

1. Shake the bottle to mix the solvents together then add it to the equipment shown on the right 2. Wait for the liquids to separate. The protactinium-234 will be in the solution in the top layer, and the uranium salt will stay in the bottom layer. Then you can point the Geiger-Müller tube at the top layer to measure the activity of the protactinium-234 3. As soon as the liquids separate, record the count rate (e.g. how many counts you get in 10 seconds) Re-measure the count rate at sensible intervals (e.g. every 30 seconds). 4. Once you've collected data, leave the bottle to stand for at least 10 minutes then take the count rate again. This is the background radiation count corresponding to the background radiation (this can be done at the beginning of the experiment before shaking the bottle as well). 5. Subtract the value from your measured count rates, then plot a graph of count rate against time. It should create a decreasing exponential curve (see page 74). You can use this to find the half life (see other cards).

Explain why there are different values for Hubble's Constant (H₀) and state some of these.

1. Since distance is very difficult to measure, astronomers used to disagree greatly in the value of H₀, with measurements ranging from 50 to 100 kms⁻¹Mpc⁻¹. 2. It is now generally accepted that H₀ lies between 65 and 80 kms⁻¹Mpc⁻, most agree it is the mid to low 70s. You'll be given a value for the exam

What does the time constant mean? See graph on page 45

1. So τ, the time constant, is the time taken for the charge, potential difference to fall to 37% of its initial value 2. It's also the time taken for the charge or potential difference of a charging capacitor to rise to 63% of it's maximum value. 3. The larger the resistor in series with the capacitor the longer it takes to charge or discharge 4. In practice the time taken for a capacitor to charge or discharge fully is taken to be about 5CR

What is the problem with using ultrasound imaging through soft tissue? What is done to solve this?

1. Soft tissue has a very different acoustic impedance from air, so almost all the ultrasound energy is reflected from the surface of the body if there is air between the transducer and the body 2. To avoid this, you need a coupling medium usually a gel) between the transducer and the body - this displaces the air and has an impedance much closer to that of body tissue. THe use of coupling media is an example of impedance matching.

Explain the life cycle of stars from the beginning up to main sequence

1. Stars are born in a cloud of interstellar dust and gas, most of which was left when previous stars blew themselves apart in a supernovae. The denser clumps of cloud contract (very slowly) under the force of gravity 2. When these clumps get dense enough the cloud fragments into regions called protostars, that continue to contract and heat up. 3. Eventually, the temperature at the centre of a protostar reaches a few million degrees, and hydrogen nuclei start to fuse together to form helium (see other notes for more on nuclear fusion). 4. As the star's temperature increases and its volume decreases (remember, its contracting), the gas pressure increases (see gas law notes). 5. There is also radiation pressure in the star - a pressure exerted by electromagnetic radiation on any surface it hits. It's usually too tiny to notice, but becomes significant in stars because of the enormous amount of electromagnetic radiation released by fusion. 6. The combination of gas pressure and radiation pressure counteract the force of gravity, preventing the star from contracting further. 7. The star has now reached the Main Sequence and will stay there relatively unchanged, while it fuses hydrogen into helium.

Explain the life cycle of stars from main sequence up to red giants

1. Stars spend most of their lives as main sequence stars. The pressure produced from hydrogen fusion in their core balances the gravitational force trying to compress them. This stage is called core hydrogen burning. 2. When the hydrogen in the core runs out, nuclear fusion stops, and with it the outward pressure stops. The core contracts and heats up under the weight of the star. The outer layers expand and cool and the star becomes a Red Giant 3. The material surrounding the core still has plenty of hydrogen. The heat form the contracting core releases the temperature of this material enough for the hydrogen to fuse. This is called shell hydrogen burning. (Very low-mass stars stop at this point. They use up their fuel and slowly fade away). 4. The core continues to contract until, eventually, it gets hot enough and dense enough for helium to fuse into carbon and oxygen. This is called core helium burning. This reduces a huge amount of energy, which pushes the outer layers of the star outwards. 5. When the helium runs out. the carbon-oxygen core contracts again and heats a shell around it so that helium can fuse in this region - shell helium burning.

For Alpha radiation give the following information: 1. Ionising Power 2. Speed 3. Penetrating Power 4. If they are affected by magnetic field

1. Strong 2. Slow 3. Absorbed by paper or a few cm of air. 4. Yes

Where would damping be used?

1. Structures are damped to avoid being damaged by resonance. 2. Loudspeakers are also made to have as flat a response as possible so they don't 'colour' the sound.

Explain the Zeorth Law of Thermodynamics

1. Suppose A, B and C are three identical metal blocks (see page 5 for diagram). A has been in a warm oven, B has come from a refrigerator and C is at room temperature. 2. Thermal energy flows from A to C and C to B until they all reach thermal equilibrium and the net flow of energy stops, This happens when the three blocks are at the same temperature.

Give the history of the universe at about 100 seconds

1. Temperature has cooled to 10⁹K. 2. The universe is similar to the interior of a star. Protons are cool enough to fuse to form helium nuclei.

Give the history of the universe at about 14 billion years (now)

1. Temperature has cooled to about 2.7K 2. Slight density fluctuations in the universe mean that, over time, clumps of matter have be condensed by gravity into galactic clusters, galaxies and individual stars.

Give the history of the universe at about 300,000 years

1. Temperature has cooled to about 3000 K. 2. The universe is cool enough for electrons (that were produced in the first millisecond) to combine with helium and hydrogen nuclei to form atoms. 3. The universe becomes transparent since there are no free charges for the photons to interact with. This process is called recombination.

(Equation +) State and explain relating Boltzmann constant, the molar gas constant and Avogadro's constant State the value of Boltzmann constant

1. The Boltzmann constant, k, is given by k = R/NA 2. You can think of the Boltzmann constant as the gas constant for one particle of gas, while R is the gas constant for one mole of gas. 3. The value of Boltzmann constant is 1.30x10⁻²³ JK⁻¹

Explain the uses and similarities and differences between the Celsius and Kelvin (thermodynamic) scales. Don't reference numeric values

1. The Celsius scale uses the freezing and boiling points of water (0°C and 100°C) to make a temperature scale which can be easily used on a day to day basis. 2. However, scientists use the kelvin scale (the absolute scale of temperature) for all equations in thermal physics 3. It is also known as the thermodynamic scale, and it does not depend on the properties of any particular substance, unlike the celsius scale.

Give the SI unit for Hubble's Constant (H₀) Explain how you can get H₀ in base units.

1. The SI unit for H₀ is s⁻¹ 2. To get H₀ in SI units, you need v in ms⁻¹ and d in m (1 Mpc = 3.1 x10²²)

Explain how we can calculate the size of the observable universe.

1. The absolute size of the universe is unknown but there is a limit to the size of the observable universe. 2. This is basically a sphere (with the Earth at its centre) with a radius equal to the max distance that light can travel during its age. 3. So if H₀ = 70kms⁻¹Mpc⁻¹, then this sphere will have a radius of 14 billion light years. Taking into account the expansion of the universe (see other cards) it is thought to be more like 46-47 billion light years.

(Equation +) Define: Acoustic Impedance (by also giving the equation) Explain the symbols

1. The acoustic impedance, Z, of a medium is defined as: Z = ρc . 2. It has units of kgm⁻²s⁻¹: Equation: Z = ρc 3. Where ρ is the density of the material and c is the speed of sound in that material

Explain the basis behind the A = λN equation

1. The activity - the number of nuclei that decay each second - is proportional to the size of the sample. For a given isotope, twice the number of nuclei will decay per second in a sample twice as large. 2. The decay constant (λ - don't confuse with wavelength) measures how quickly an isotope will decay the bigger the value of λ he faster the rate of decay. The unit is s⁻¹

Explain what an A-Scan is (See diagram on page 85)

1. The amplitude scan (A-Scan) sends a short pulse of ultrasound into the body simultaneously with an electron beam sweeping across a cathode ray oscilloscope (CRO) screen. 2. The scanner receives reflected ultrasound pulses that appear as vertical deflections on the CRO screen. Weaker pulses (that have travelled further in the body and arrive later) are amplified more to avoid the loss of valuable data - this process is called time-gain compensation (TGC) 3. The horizontal positions of the reflected pules indicate the time the 'echo' took to return, and are used to work out distances between structures in the body (e.g. the diameter of a baby's head in the uterus). 4. A stream of pules can produce a steady image on the screen, although modern CROs can store a digital image after just one exposure

Using the binding energy graph on page 77, calculate the energy released for fission of when ²³⁵U is split into ⁹²Rb and ¹⁴⁰Cs (Plus a few neutrons)

1. The binding energy before the fission is binding energy ²³⁵U = 235 x 7.4 = 1739 MeV 2. The binding energy after fission is binding energy ⁹²Rb + binding energy ¹⁴⁰Cs = (92 x 8.8) + (140 x 8.2) = 1957.6 MeV 3. So the energy released is 1957.6-173 = 218.6 = 220 MeV (to 2 s.f.)

Using the binding energy graph on page 77, calculate the energy released when ²H and ³H fuse together to form ⁴He (and a neutron)

1. The binding energy before the fusion is: binding energy ²H + binding energy ³H = (2 x 1.1) + (3 x 2.6) = 10 meV 2. The binding energy after the fusion is binding energy ⁴He = 4 x 6.8 = 27.2 MeV 3. So the energy released is: 27.2-10 = 17.2 = 17 MeV (to 2 s.f.)

Explain what affects the capacitance of a capacitor

1. The capacitance (p.40) of a capacitor depends on how easy it is to generate an electric field between two plates 2. It also depends on the dimensions of the capacitor.

Explain how the time taken to charge or discharge a capacitor is affected by the capacitance and resistance

1. The capacitance of a capacitor (C) affects the amount of charge that can be transferred at a given voltage 2. The resistance of the circuit (R). This affects the current in the circuit.

(Equation +) Explain why the formula for charging and discharging current of a capacitor is the same

1. The charging current decreases exponentially (it travels in the opposite direction to the discharging current). 2. So the formula for the charging current at a given time is the same as for a discharging capacitor: I = I₀e^(-t/CR)

Give some key points about Maxwell-Boltzmann graphs (as shown on page 12)

1. The curve starts at (0,0) as no molecules have zero energy 2. Most molecules are moving at a moderate speed so their energies are within the main section 3. Relatively few molecules are moving slowly (they are in the bottom left section). 4. Relatively few molecules are moving quickly (they are in the bottom right section)

In terms of SHM, explain the displacement and the restoring force

1. The distance of the object from the midpoint is called the displacement 2. There is always a restoring force pulling or pushing the object back towards the midpoint 3. The size of the restoring force depends on the displacement, and the force makes the object accelerate towards the midpoint.

What useful information can be taken from PET scans? What can this be used to diagnose

1. The distribution of radioactivity matches up with metabolic activity. This is because more of the radioactive glucose (or whatever) injected into the patient is taken up and used by the cells that are doing more work (cells with an increased metabolism, in other words). 2. By looking at which cells are doing more work, doctors can help diagnose illnesses in patients - like detecting the higher activity of cancer cells (see other cards).

Explain what happens (physics wise) when a capacitor when it is discharged

1. The electrons (current) flow from the negative plate to the positive plate. 2. Initially, the current is high, but as the charge leaves the plates, the potential difference across the plates decreases. 3. Therefore, the electrostatic repulsion decreases, reducing the flow of current.

Define/Explain what escape velocity is

1. The escape velocity is defined as the velocity needed so an object has just enough kinetic energy to escape a gravitational field. 2. This is when an object's kinetic energy is equal and opposite to its gravitational potential energy - so the total energy is 0.

Explain the diagram on page 47 (Also make sure you are happy with drawing diagrams in textbook page 427)

1. The field lines are parallel to each other 2. Areas with the same potential are parallel to the plates, and perpendicular to the field lines.

When doing an experiment to find the specific heat capacity of a material, what is important to note about the final value? What can be done to solve this?

1. The final value for C will be a large overestimate. (Note that this is not always the case in all experiments (e.g. starting at a low temperature. etc. ). 2. This is because some of the energy from the heater gets transferred to the air and the container. 3. This source of error can be decreased by starting below and finishing above room temperature to cancel out gains and losses. 4. Temperature will continue to rise when turned off - so if using the non graph method, it is important to continue noting temperature rise until it begins to fall again once the heater is switched off.

Explain the forces experienced on an 2 objects in a gravitational field

1. The force experienced by an object in a gravitational field is always attractive. It's a vector which depends on the masses involved and the distance between them. 2. The diagram on page 22 shows the force acting on mass m due to mass M. (The force on M due to m is equal and in the opposite direction 3. M an m are uniform spheres which behave as point masses (as it all mass is concentrated at the centre.

Explain Coulomb's Law Give the value for ε₀

1. The force on Q is always equal and opposite to the force on q 2. It's an inverse square law (like with gravitational attraction). The further apart the charges are the weaker the force between them 3. The size of the force F also depends on the permittivity, ε, of the material between the two charges. For free space (a vacuum) the permittivity is ε₀ = 8.85 x10⁻¹² C²N⁻¹m⁻² or Fm⁻¹

Give the assumptions in the kinetic model

1. The gas contains a large number of particles. 2. The particles move rapidly and randomly. 3. The volume of the particles is negligible when compared to the volume of the gas. 4. Collisions between particles themselves or between particles and the walls of the container are perfectly elastic. 5. The duration of each collision is negligible when compared to the time between collisions 6. There are no forces between particles except for the moment when they are in collision.

Explain how a capacitor discharging decreases exponentially

1. The graph of a capacitor discharging (and that from iterative modeling) is essentially one of exponential decay (see page 86/notes on Nuclear Decay). 2. This means that when a capacitor is discharging, the amount of charge left on the plates falls exponentially with time. 3. It always takes the same length of time for the charge to halve, no matter how much charge you start with - like radioactive decay. 4. For a given proportion, it always takes the same time for that proportion of the charge to be lost - it's known as the constant ratio property of exponential relationships.

Explain the graph of Force v. Distance on page 24

1. The graph shows how the force on an object, due to gravitational field of a point mass, varies with the object's distance, r, from the point mass. 2. The area under the curve between the two values of r gives the work done to move the object from one point to the other

Explain what gravitational potential is (g) are subscript)

1. The gravitational potential V(g), at a point is the work g in moving a unit mass from infinity to that point

Describe and explain what can be used to describe matter Why was this not accepted at first?

1. The idea that solids, liquids and gases are made up of tiny moving or vibrating particles is called the kinetic model of matter. 2. It seems obvious now, but this wasn't always accepted by the scientific community. It took several scientists and hundreds of years to develop a controversial idea into an accepted theory

State and explain the various energies that makeup Internal Energy

1. The kinetic energy of a particle depends on its mass and speed. Through kinetic theory, the average kinetic energy is proportional to temperature - the hotter the temperature, the higher the average kinetic energy 2. Potential energy is caused by interactions between particles and is based on their positions relative to each other These energies are randomly distributed amongst the particles

Explain What Binding Energy Is

1. The mass of a nucleus is less than the mass of its constituent parts - the difference is called the mass defect. They are equivalent according to Einstein's equation: ∆E = ∆mc² 2. As nucleons join together, the total mass decreases - this 'lost' mass is converted into energy and released. This energy can be calculated with the above equation. 3. The amount of energy released is equivalent to the mass defect 4. If you pulled the nucleus completely apart, the energy you'd have to use to do it would be the same as the energy released when the nucleus is formed.

What is rest mass?

1. The mass of the particle when it's not moving. 2. This is because the masses of objects charge when they are moving at very high speeds (you don't need to worry about this).

What governs the maximum energy of the X-ray tube?

1. The maximum energy of the X-ray photons is equal to the potential difference of the X-ray tube x by the charge of an electron. 2. So if a potential difference of 50 kC is used in the tube, the max X-ray energy will be 50 keV.

Explain how neutrons decay Give the equation

1. The neutron is an unstable particle that decays into a proton. (But it's much more stable when part of the nucleus.) 2. It's really just an example of β⁻ decay caused by the weak nuclear force. n→p + e⁻ + ν (ν has bar over the top) 3. Free neutrons (i.e. those not held in a nucleus) have a half life of around 15 minutes.

Explain the role of the nucleus in radioactive decay.

1. The nucleus is under the influence of the strong nuclear force holding it together and the electrostatic force pushing the protons apart. It is a very delicate balance, and it's easy for a nucleus to become unstable. 2. If a nucleus is unstable, it will break down to become more stable. 3. The nucleus decays by releasing energy and/or particles (nuclear radiation) until it reaches a stable form. This is called radioacive decay

(Equation) State and explain the equation that links number of particles, number of moles and Avogadro's constant

1. The number of particles, N, in an amount of gas is given by the number of moles, n, multiplied by Avogadro's constant, NA (6.02x10²³) 2. Equation: N = n x NA

What is the proton number? What is it sometimes called? Give its symbol

1. The number of protons in the nucleus 2. Also called the atomic number 3. Has the symbol Z

(Equation +) Explain how to calculate the work done by a capacitor from a graph Give the equation as well and Units

1. The p.d. across the capacitor is proportional to the charge stored on it, so the graph will be a straight line through the origin. The energy stored is given by the yellow triangle (shown on the graph on page 42). 2. Equation is Area of triangle = 1/2 x base x height so the energy stored by a capacitor is: W = 1/2QV W = Work Done (Joules, J), Q = Charge (Coulombs, C), V = Potential Difference (Volts, V)

Explain how CAT/CT scans work

1. The patient lies on a table, which slides out of a ring .This ring is made up of detectors and a rotating X-ray beam 2. The X-ray beam fans out and rotates around the body. It is picked up by the detectors. 3. A computer works out how much attenuation has been caused by each part of the body and produces a high quality image.

What is special about the potential energy of an ideal gas?

1. The potential energy of an ideal gas is 0J because there are no forces between the particles. 2. This means the internal energy is equal to the total random kinetic energy only (see page 4 or above cards).

Explain the role of the proton number/atomic number and the relationship between electrons and protons in a neutral atom

1. The proton number defines the element - no two elements have the same number of protons 2. In a neutral atom, the number of electrons equals the number of protons. The elements reactions and chemical behaviour depend on the number of electrons. So the proton number tells you a lot about its chemical properties.

Explain why you can see distinct areas on a H-R graph and why you don't see stars in any transitional period.

1. The reason you can see distinct areas is because stars exist i these stable stages of their life cycle for long periods of time. 2. You don't see groups of stars in any transitional period on the H-R diagram because they are unstable and transitions happen quickly (compared with the life of the star)

Explain what is special about the formula V = Q/(4πε₀r)

1. The sign of V depends on the charge Q - i.e. : A. V is positive when Q is positive and the force is repulsive (when acting on a unit positive charge). B. V is negative when Q is negative the force is attractive. 2. The absolute magnitude of V is the greatest on the surface of the charge and decreases as the distance from the charge increases.

In relation to the graph on page 64, compare the strong nuclear and electrostatic forces by explaining how they changes as the distance of separation between them changes

1. The strong nuclear force is repulsive for very small separations of nucleons (below about 0.5 fm). 2. As nucleon separation increases past about 0.5 f, the strong nuclear force becomes attractive. It reaches a maximum value and then falls rapidly to zero. After about 3 fm it can no longer hold nucleons together 3. The electrostatic repulsive force extends over a much larger range (indefinitely actually).

Explain how the ionising power links to the range of radiation

1. The stronger the ionising power of radiation, the more energy it loses in a given distance. 2. The shorter the range of radiation.

(Equation +) Derive the equation relating Time Period, Mass and radius of a satellite.

1. The time taken for one orbit is called the period, T (in seconds). For circular motion T = (2πr)/v . 2. Substituting this into v = √(GM/r) and rearranging gives: * T² = (4π²/GM)r³

What is the nucelon number? What is it sometimes called? Give its symbol

1. The total number of protons and neutrons in the nucleus 2. Also called the mass number 3. Has the symbol A

How is the tracer used in medicine? What affects where the tracer goes?

1. The tracer is injected into or swallowed by the patient and then moves through the body to the region of interests. 2. Where the tracer goes depends on the substance and the isotope is bound to - i.e. it goes anywhere that the substance would normally go, and is used how that substance is normally used.

Explain how the restoring force in SHM exchanges PE and KE (See graphs in page 16 for more info)

1. The type of potential energy (PE) depends on what it is providing the restoring force - e.g. gravitational PE for pendulums or elastic PE (elastic stored energy) for masses on springs moving horizontally. 2. As the object moves towards the midpoint, the restoring force does work on the object and so transfers some PE to KE. When the object is moving away form the midpoint, the object's KE is transferred back to PE again. 3. As the object passes the midpoint, its PE is zero and its KE is maximum. 4. At the maximum displacement (the amplitude) on both sides of the midpoint, the object's KE is zero and its PE is at is maximum. 5. The sum of the potential and kinetic energy is called the mechanical energy and stays constant (as long as the motion isn't damped - see later). 6. The energy transfer for one complete cycle of oscillation is: PE to KE to PE to KE to PE and the process repeats

What quarks are needed to make protons and neutrons? Name another quark that you need to know

1. The up quark (u) and the down quark (d) 2. The strange quark (s)

In terms of SHM - what other factors can be tested that affect it? State their expected results and what needs to be done to make sure the experiment is fair.

1. The weight of the mass - the heavier the mass, the longer the time period 2. The stiffness of the spring - the stiffer the spring the shorter the time period 3. The size of the initial displacement - which should have no effect on time period. Fair Test: Repeat experiment many times + control all other factors not being tested.

Give some advantages to using ultrasound imaging

1. There are no known hazards - in particular no exposure to ionising radiation 2. It's good for imaging soft tissues since you can obtain real time images 3. Ultrasound devices are relatively cheap and portable 4. The scan is a quick procedure (10-15 minutes) and the patient can move during the scan

What happens during gamma emission in terms of nuclear constituents and energy?

1. There is no change to the nuclear constituents 2. The nucleus just loses excess energy

State and describe the properties of neutrinos

1. They have zero (or almost zero) mass and zero electric charge - so they don't do much 2. They can only take part in weak interactions 3. A neutrino can pass right through the earth without anything happening to it.

Explain the doppler effect in relation to light

1. This happens with light too - when a light source moves away from us, the wavelengths become longer and the frequencies become lower. 2. This shifts the light towards us, the opposite happens and the light undergoes blue shift.

Explain the difference between spontaneous fission and induced fission and what affects it.

1. This process is spontaneous if it just happens by itself, or induced if we encourage it to happen. 2. The larger the nucleus, the more unstable it will be - so large nuclei are more likely to spontaneously fission. 3. This means that spontaneous fission limits the number of nucleons that a nucleus can contain - in other words, it limits the number of possible elements.

Explain the Strong Nuclear Force and give various properties of it

1. To hold the nucleus together, the strong nuclear force must be an attractive force that overcomes the electrostatic force (the repulsive force between the positive charges of the protons - see notes on electromagnetic fields). 2. Experiments have shown that the strong nuclear force between nucleons has a short range. It can only hold nucleons together when they are separated by up to a few femtometers - the size of a nucleus. 3. The strength of the strong nuclear force between nucleons quickly falls beyond this distance 4. Experiments also show that the strong nuclear force works equally between all nucleons. This means that the size of the force is the same whether proton-proton, neutron-neutron or proton-neutron. 5. At very small separations, the strong nuclear force must be repulsive - otherwise there would be nothing to stop it crushing the nucleus to a point.

Explain the latent heat of fusion

1. To melt a solid, you need to break the bonds that hold the particles in place. 2. The energy needed for this is called the latent heat of fusion

Explain what Gravitational potential difference is

1. Two points at different distances from a mass will have different gravitational potentials (because the magnitude of the gravitational potential decreases with distance) - this means that there is a gravitational potential difference between those two points. 2.When you move an object you do work against gravity - the amount of energy you need depends on the mass of the object and the gravitational potential difference you move it through.

Give some disadvantages to using ultrasound imaging

1. Ultrasound doesn't penetrate bone - so it can't be used to detect fractures or examine the brain 2. Ultrasound cannot pass through air spaces in the body (due to the mismatch in impedance) - so it can't produce images from behind the lungs 3. It can't give detail on solid masses 4. Ultrasound can't give information about any solid masses found

Explain how Ultrasound Waves are Affected by the Doppler Effect

1. Ultrasound waves are reflected at an angle to moving cells undergo a change of frequency (or wavelength). This is caused by the Doppler effect (page 36). 2. This change of frequency (beat frequency) can allow doctors to find the speed at which those cells are moving (for example, blood cells in an artery).

Explain how red shift shows the galaxy is expanding∆λ/λ = ∆

1. Until the early 20th century, cosmologists believed that the Universe was infinite in both space and time (that is, it had always existed) and static. 2. This changed when Edwin Hubble released that the spectra form galaxies (apart from a few very close ones - some which show blue sift as they are coming towards us due to gravitational attraction) all show red shift - so they're all moving away from us. The amount of galactic red shift gives the recessional velocity - how fast the galaxy is moving away.

Give the symbol and relative charge for the following quarks: 1. Up 2. Down 3. Strange

1. Up, U, +2/3 2. Down, d, -1/3 3. Strange, s, -1/3

Explain where Fluorine-18 is used and why in the context of medical tracers

1. Used in PET scans as It undergoes beta plus decay 2. Has a half-life of 110 minutes meaning the patient is exposed to radioactivity for a much shorter amount of time, than technetium-99m

Explain how to derive d = r/θ (See diagram on page 29 and ensure you understand it)

1. Using trig: d = r/tanθ 2. θ is really small for stars so you can use a small angle approximation tanθ = θ (where θ is in radians) 3. So d = r/θ

(Equation) Give the formulas for voltage + current of a discharging capacitor. Explain symbols and give units

1. V = V₀e^(-t/CR) 2. I = I₀e^(-t/CR) Where V₀/I₀ is the voltage/current of the capacitor when it's fully charged (C) t is the time since discharging began (s) R is the resistance (Ω) C is the capacitance (F)

For Gamma radiation give the following information: 1. Ionising Power 2. Speed 3. Penetrating Power 4. If they are affected by magnetic field

1. Very weak 2. Speed of light 3. Absorbed by many cm of lead and several of concrete 4. No

(Equation +) Give 2 more forms of the equation: W = 1/2QV and explain how you got them

1. W = 1/2V²C - This is Q = CV subbed into the original. 2. W = 1/2 * Q²/C - This is V = Q/C subbed into the original equation

For Beta-minus (beta) radiation give the following information: 1. Ionising Power 2. Speed 3. Penetrating Power 4. If they are affected by magnetic field

1. Weak 2. Fast 3. Absorbed by ∼3 mm of aluminium 4. Yes

Explain how X-ray's are attenuated when they pass through matter

1. When X-rays pass through matter (e.g. a patients body) they are absorbed and scattered. 2. The intensity (I) of the X-ray beam decreases (attenuates) exponentially with distance from the surface (x), according to the materials attenuation (absorption) coefficient (µ).

What happens when a capacitor is charged? (E.g. how do they work) (See Page 40)

1. When a capacitor is connected to a power source, positive and negative charge build up on opposite plates. 2. The insulating material (which could be an air gap) stops charge moving between the two plates so a potential difference is created (which is incidentally the potential difference between two points is the work done in moving a unit charge between them). 3. This creates a uniform electric field between the plates

Explain how ultrasound works

1. When an ultrasound wave meets a boundary between two different materials some of it is reflected and some of it passes through (undergoing refraction if the angle of incidence is not 90°) 2. The reflected waves are detected by the ultrasound scanner and are used to generate an image

Explain the process of pair production and the result of it See diagram on page 66

1. When energy is converted into mass, you get equal amounts of matter and antimatter: 2. Fire two protons at each other at high speed and you'll end up with a lot of energy at the point of impact. This energy might be converted into more particles 3. If an extra proton is formed then there will always be an antiproton to go with it. It's called pair production

Explain how radioactive waste is disposed and the issues surrounding this.

1. When material is removed from the reactor, it is initially very hot, so it is placed in cooling ponds until the temperature falls to a safe level. 2. The radioactive waste is then stored in sealed containers in specialist facilities until its activity has fallen sufficiently. 3. This can take many years and there is a risk that the material could escape from these containers. A leak of radioactive material could be armful to the environment and local human populations, both now and in the future, particularly if the material contaminated water supplies.

Explain the latent heat of vaporaisation

1. When you boil or evaporate a liquid, energy is needed to pull the particles apart completely. 2. This is the latent heat of vaporisation

Explain what happens to energy during a change in phase. Give an example

1. When you heat a substance, you increase its temperature - thereby increasing the kinetic energy of the particles within it and its internal energy. 2. When a substance changes phase, its internal energy changes, but its kinetic energy (and temperature) doesn't. This is because the change of phase is altering the bonds and therefore potential energy of the particles. 3. For example, in a pan of boiling water, the potential energy of the water molecules increases as they break free of the liquid. But the water in both places is at 100°C

Describe and explain what happens when two or more capacitors are placed in series.

1. When you put capacitors in a series circuit, the potential difference is shared between them 2. Each capacitor stores the same charge 1/Ctotal = 1/C₁ + 1/C₂ ...

Explain the energy changes in relation to Capacitors

1. Work is done by removing negative charge from one plate and depositing it onto the other plate (to charge the capacitor). The energy for this must come from the electrical energy of the battery, and is given as charge x average p.d. 2. The energy stored by a capacitor is equal to the work done by the battery. So, you can find the energy stored from the area under a graph of p.d., against charge stored on the capacitor.

Describe and explain another way of producing X-rays (See diagram on page 80)

1. X-rays are also produced when beam electrons knock out other electrons from the inner shells of the tungsten atoms 2. Electrons in the atom's outer shells move into the vacancies in the lower energy levels and release energy in the form of X-ray photons.:

Describe and explain an experiment that you can do to investigate pressure and volume (Boyle's Law) (See Page 8 for diagram)

1. You can investigate the effect of pressure on volume by setting up the experiment shown on page 8. The oil confines a parcel of air in a sealed tube with fixed dimensions. A tyre pump is used to increase the pressure in the tube and the Bourdon gauge records the pressure. As the pressure increases the air will compress and the volume occupied by the tube will reduce 2. Measure the volume of air when the system is at atmospheric pressure, then gradually increase the pressure noting down both the pressure and the volume of air Multiplying them together at any point should give a constant.

(Equation +) Derive the equation: R = r₀A¹/³ (Slash is superscript) Give the value of r₀

1. You can measure the size of a nucleus by firing particles at it. If you plot the radius of the nucleus, R, against the nucleon number, you get a graph like that on page 62 - a curve. 2. In fact, the nuclear radius increases roughly as the cube root of the nucleon number. You can see this by plotting nuclear radius against the cube root of the nucleon number (see page 62). The straight line through the origin shows that the nuclear radius is directly proportional to the cube root of the nucleon number. In other words: R α AA¹/³ 3. By introducing a constant, r₀, we can make the following equation: R = r₀A¹/³ Where r₀ is 1.4 x 10⁻¹⁵ m (1.4 fm)

Explain how comparing the emission and absorption spectrums is useful in the context of stars

1. You get absorption line in the spectra of light from stars. Stars can be assumed to emit radiation in a continuous spectrum. Thi radiation has to pass through a large amount of gas at the surface of the star (the star's 'atmosphere') before travelling to Earth. This gas absorbs particular wavelengths of light depending on the elements it consists of. 2. Comparing the absorption spectra of stars to sets of emission spectral lines from the lab therefore allow you to identify elements within a star 3. The most common element in most stars is hydrogen, so the spectral lines for hydrogen are usually the clearest. This makes these lines the easiest to identify and measure.

Describe and explain the expected outcomes from a test of SHM with data loggers etc.

1. You should find the amplitude of the oscillations gets smaller over time by the time period remains constant. 2. If you leave the system oscillating for long enough, the amplitude will decrease until the mass eventually comes to a rest. This is because energy is lost to overcoming air resistance as the mass moves up and down.

Explain 'critical mass' in terms of a nuclear reactor. (See diagram on page 78)

1. You want the chain reaction to continue on its own at a steady rate, where one fission follows another. 2. The amount of 'fuel' you need to do this is called the critical mass - any less than the critical mass (subcritical mass) and the reaction will just peter out. 3. Nuclear reactors use a supercritical mass of fuel (where several new fissions normally follow each fission) and control the rate of fission using control rods.

(Equation) Give the two equations for centripetal acceleraton

1. a = v²/r or centripetal acceleration = linear velocity squared/radius of circle 2. a = ω²r or centripetal acceleration = angular velocity/radius

(Equation +) Give the equations for finding a distance to a nearby star in parsecs Explain how to remember it Give teh value of one parsec

1. d = 1/p or p = 1/d (where p is the angle of parallax in arcseconds) 2. The clue is in the name really - 1 parsec away if the parallax is 1 arcsecond) 3. One parsec is about 3.1 x 10¹⁶ m. The nearest star to Earth (other than the Sun) is about 1.3 parsecs away.

Explain the role of the moderator in a nuclear reactor What is important to consider when choosing a moderator? (See diagram on page 78)

1. ²³⁵U fuel rods need to be placed in a moderator (for example, water) to slow down and/or absorb neutrons. 2. You need to choose a moderator that will slow down some neutrons enough so they can cause further fission, keeping the reaction going at a steady rate.

For Alpha radiation give the following information: 1. It's symbol 2. The Constituent 3. Relative Charge 4. Mass (u - atomic mass unit)

1. α 2. A Helium nucleus - 2 protons and 2 neutrons 3. +2 charge 4. 4

For Beta-minus (beta) radiation give the following information: 1. It's symbol 2. The Constituent 3. Relative Charge 4. Mass (u - atomic mass unit)

1. β or β⁻ 2. Electron 3. -1 4. Negligible

For Beta-plus radiation give the following information: 1. It's symbol 2. The Constituent 3. Relative Charge 4. Mass (u - atomic mass unit)

1. β⁺ 2. Positron 3. +1 4. Negligible

(Equation +) State and explain the equation used for diffraction gratings

4. If you know the slit separation, d, the order of the maximum you're observing, n, and the angle between this maximum and the incident light, θ, you can find the wavelength of the incident light: dsinθ = nλ (note that if sinθ > 1 then that maximum doesn't exist)

Explain how you will analyse your findings in an experiment to investigate circular motion. (2/3 of experiment) (Some W's are subscript - see page 15 for clarity)

5. You can use the formula ω = 2π/T to find the angular velocity of the bung, and F =mbω²r to find the centripetal force. In this equation, r is the radius of the circle which should be the distance from the reference mark on the string to the centre of the bung. 6. The centripetal force should be equal to the weight of the washers (w = mwg) 7. Repeat this experiment for different distances between the bung and the reference mark - you should find that as r gets bigger, the time period gets longer but the centripetal force stays the same.

(Equation) Give an equation to show how a sample's activity goes down as it decays. Give Units

A = A₀e^-λt A is the activity at time t, and A₀ is the initial activity (at t = 0 s). Both are measured in Bq

What is the only stable hadron?

A Proton

Explain Pair Production as a way of attenuating X-rays

A high (> 1.1 MeV) energy photon decays into an electron and a positron

Explain Compton scattering as a way of attenuating X-rays

A photon with around 0.5-5 MeV of energy knocks an electron out of an atom which causes the photon to lose energy and be scattered

Define: 1 Parsec

A star is exactly one parsec (pc) away from Earth if the angle of parallax, θ, as the earth moves through 1 AU, is 1 second of arc - that's (1/3600)°

What are the advantages and disadvantages of PET scanning?

ADV: 1. PET scanners allow patients to be diagnosed without having to have surgery and radiotracers used have a short half-life so the patient is exposed to radiation for only a short time. DIS: 1. Short time period means there is only a limited time when a patient can be scanned - unlike with gamma cameras where the tracer takes a lot longer to decay. 1. PET scanners are also incredibly expensive, meaning not many hospitals own one. This means some doctors may have to make difficult decisions about whether a patient should be sent to one or not.

What are the advantages and disadvantages of satellites?

ADV: 1. These satellites are really useful for sending TV and telephone signals and have improved communication around the world. 2. The satellite is stationary relative to a certain point on the Earth so you don't have to alter the angle of your receiver (or transmitter) to keep up. DIS: 1. Expensive 2. Pose a small risk of something going wrong and the satellite falling back to earth

Explain the acceleration graph for SHM on page 16

Acceleration, a, is the gradient of the velocity-time graph. It has a maximum value of ω²A, and is in antiphase (180 degree difference) with the displacement.

(Equation) Give an equation relating Activity, decay constant and number of undecayed nuclei Give units

Activity = decay constant x number of undecayed nuclei OR A = λN Units: A is measured in becquerels (Bq), Decay Constant is measured in s⁻¹ and number of undecayed nuclei has no unit

What does 1 becquerel (Bq) mean?

An activity of 1 Bq means that 1 nucleus decays per second (s⁻¹)

What is an isotope?

An atom with the same number of protons but different number of neutrons are called isotopes

What do CAT/CT scans produce?

An image of a two-dimensional slice through the body

What is special about how radioactive decay occurs?

An individual radioactive decay is spontaneous and random - it can't be predicted

In terms of quarks,, what are antiparticles made up of?

Antiparticles of hadrons (like antiprotons and antineutrons) are made from anti-quarks

What does the area of a Current against Time graph show? (Ensure you are familiar with the graphs on page 41)

Area = i x t = charge

Explain the energy at zero Kelvin

At 0 K all particles have the minimum possible internal energy - everything theoretically stops - at higher temperatures, particles have more energy. (In fact with the Kelvin Scale, a particles energy is proportional to temperature (see later cards/page 13)).

(Equation +) Describe and explain the Pressure law, giving the equation. (See graph on page 8)

At a constant volume the pressure, p of a gas is directly proportional to its absolute temperature T Equation: p/T = Constant or Pressure/Time = Constant

(Equation ish) What is atomic mass given in units wise? Explain how to convert this to KG)

Atomic mass is usually given in atomic mass units (u) , where 1 u = 1.661x10⁻²⁷kg.

(Equation +) Explain an equation relating the activity, and the change in the number of undecayed nuclei.

Because the activity, A, is the number of nuclei that decay each second, you can write it as the charge in the number of undecayed nuclei ∆N, during a given time (in seconds), ∆t.: A = −(∆N/∆t) (The negative sign is because ∆N is always a decrease

Give the history of the universe from the Big Bang to 10⁻⁴³ seconds

Before 10⁻⁴ seconds after the big bang,This is mainly guess work. There are plenty of theories. Here is what the general consensus is at the moment: 1. Big Bang to 10⁻⁴³ seconds: Anybody's guess really. At this sort of size and energy, even general relativity stops working properly. This is the 'infinitely hot, infinitely small, infinitely dense' bit

(Equation +) Explain how the binding energy per unit mass of defect can be calculated. Give Units Give the value of mass defect of 1 u

Binding energy per unit mass of defect = binding energy/mass defect Units - MeVu⁻¹ (As Calculated on page 76) A mass defect of 1 u is equivalent to about 930 MeV (to 2 s.f.) of binding energy.

Explain how the temperature affects the speed distribution of gas particles

Both of the curves on the right of page 12 represent the same number of particles but the cooler curve has a higher, steeper peak at a lower speed. As the temperature of the gas increases: 1. The average particle speed increases 2. The minimum particle speed increases 3. The distribution of the curve becomes more spread out. (The area of both will be the same)

How are x-rays attenuated? State 3 causes of this

By absorption and scattering. There are 3 causes of this: 1. The Photoelectric Effect 2. Compton Scattering 3. Pair Production

(Equation) Give the formula relating charge, capacitance and Voltage Give Units

C = Q/V Where: C = Capacitance in Farads (F) - 1 farad = 1 CV⁻¹ Q = Charge in coulombs V = The potential difference in volts

(Formula +) Give the formula relating capacitance to the area and distance between plates. Explain terms and give units

C = ε₀A/d Where A is the area of the plates (m²), ε₀ is the permittivity of free space (Fm⁻¹), and d is the separation of the plate (m).

(Equation) What can be done to binding energy in order to look at it easier?

Calculating the binding energy per nucleon: Binding energy per nucleon (in MeV) = Binding energy (B) / Nucleon Number (A)

What produces centripetal acceleration? Explain how this works and what causes it

Centripetal force: 1. From Newton's 1st law, if an object has an acceleration, there must be a net force acting on it 2. An object will travel in a circular path if there is a constant net force acting on it perpendicular to its velocity. 3. This is called centripetal force and it always acts towards the centre of the circle.

(Equation +) Give an equation combining A = −(∆N/∆t) and A = λN

Combining these two equation for the activity then gives the rate of change of the number o undecayed nuclei: −(∆N/∆t) = λN −(∆N/∆t) = rate of change of number of undecayed nuclei N = number of undecayed nuclei in sample λ = decay constant

What does CAT or CT stand for?

Computarised Axial Tomography

Define: What is the condition needed for SHM?

Condition for SHM: An oscillation in which the acceleration of an object is directly proportional to its displacement from the midpoint, and is directed towards the midpoint.

Explain what continuous spectra are (See diagram on page 33)

Continuous Spectra contain all possible Wavelengths 1. The spectrum of white light is continuous 2. If you split white light up with a diffraction grating, the different wavelengths within the white light are diffracted by different amounts 3. Each order in the pattern becomes a spectrum, with red on the outside and violent on the inside. The zero order maximum stays white because all the wavelengths just pass straight through. 4. Hot things emit a continuous spectrum in the visible and infrared regions. If an object is hot enough, the spectrum can reach into shorter wavelengths, like ultraviolet.

Ensure you are happy with orbital calculations on (page 26)

Coool

How does P.D. and Current change when a capacitor discharges?

Current and potential difference also decrease exponentially as a capacitor discharges.

Give a rough number for how much dark matter there is in the universe

Current estimates say there is about 5 times as much dark matter as ordinary matter in the universe, and that dark matter makes up 25% of the universe in whole.

Explain some of the disadvantages of nuclear power stations

Deciding whether or not to build a nuclear power station (and if so where) is rather tricky: 1. Some waste products of nuclear fission are highly radioactive and difficult to handle and store - see extra card on storing waste 2. Accidents or natural disasters can be a problem - see extra card 3. Because of all the necessary safety precautions, building and decommissioning nuclear power plants is very time-consuming and expensive.

What do gamma cameras do?

Detect the γ-rays emitted by radiotracers injected into a patient's body

Explain the displacement graph for SHM on page 16

Displacement, x, varies with time, t, as a cosine (or sine) wave with a maximum value, A, (the amplitude)

(Equation +) State what all of the symbols represent in the following equation: 1/2Nmc² = 3/2NkT (with bar above c²)

E = 3/2kT c² = mean squared speed of particles N = number of particles in the gas m = mass of one particle T = absolute temperature k = 1.38 x10⁻²³ JK⁻¹ (Boltzmann constant)

State and explain 2 formulas for the Electric Potential energy

E = Vq and E = Qq/(4πε₀r) Where E is the electric potential energy (J) V is the electric potential (V) Q is the size of the charge in the electric field . (Don't confuse this with the E for electric field strength found in other cards and page 46)

(Equation) Give the equation for Specific Latent Heat Give the Units What is L sometimes written out as?

E = mL or energy change = mass of substance changed x specific latent heat Units of L: J kg⁻¹ L is usually written as Lv for latent heat of vaporization and Lf for latent heat of fusion.

(Equation) Give the equation for Specific Heat Capacity What are the units? How is the formula sometimes subtly different?

E = mcΔθ or Energy change = mass x specific heat capacity x change in temperature Units: Jkg⁻¹K⁻¹ or Jkg⁻¹°C⁻¹ Q is sometimes used instead of E for the change in thermal energy

Explain when pair production happens and the results of it (See diagram on page 66)

Each Particle-Antiparticle pair is produced from a single photon 1. Pair production only happens if one one photon has enough energy to produce that much mass. It also tends to happen near a nucleus, which helps conserve momentum 2. You usually get electron-positron pairs produced (rather than any other pair) - because they have a relatively low mass. 3. The minimum amount of energy the photon must have is the combined energy of the two particles at rest (i.e. assuming that the particles have negligible kinetic energy).

State Kepler's First Law See diagram on page 27

Each planet moves in an ellipse around the Sun, with the Sun at one focus (a circle is just a special kind of ellipse).

What can particles mean in a gas?

Either molecules or atoms

(Equation +) Define Electric Field Strength

Electric field strength, E, is defined as the force per unit positive charge - the force that a charge of +1 C would experience in the electric field: E = F/Q (Where F is the force acting on a charge Q which is in the electric field. Here, Q, is not causing the electric field .Don't confuse it with the Q in the section below)

Give the Symbol, Relative Charge and Rest Mass (kg) of a Electron and it's relative Antiparticle (stating the name).

Electron: Symbol = e⁻ Relative Charge = -1 Rest mass = 9.11 x 10⁻⁻³¹ kg Positron: Symbol = e⁺ Relative Charge = +1 Rest mass = 9.11 x 10⁻⁻³¹ kg

Explain how you will do an experiment to investigate circular motion. (1/3 of experiment) (Some W's are subscript - see page 15 for clarity)

Equipment: Rubber bung, some washers, some string, and a glass tube. 1. Measure the mass of the bung (mb) and the mass of the washers (mw), the attach the bung to the string. Thread the string through the glass tube, and weigh down the free end using the washers. 2. Make a reference mark on the string, then measure the distance from the mark to the centre of the bung. Pull the string taut to make sure this measurement is as accurate as possible 3. Line the mark up with the top of the glass tube, then begin to spin the bung in a horizontal circle (see diagram on page 15). You will need to spin it at the right speed to keep the reference mark level with the top of the glass tube (spin too quickly and it will move outwards, too slowly it will move down). Try to keep your hand still as possible whilst you spin. 4. Measure out the time taken for the bung to make one complete circle. This is the time period, T. In practice this may be too small to time accurately, so you might need to measure the time taken to complete ten circles and then get an average

(Equation) Give Newton's Law of Gravitation Explain the origin of the negative sign

F = -(GMm)/r² or Force (acting on mass m due to M) = (the gravitational constant - 6.67x10⁻¹¹ Nm²kg⁻² x Mass 1 x mass 2)/(RadiusSquared) The negative sign shows that vector F is in the opposite direction to r (displacement of m from M)

Be sure you are familiar with the Maxwell-Boltzmann graph on page 12 CGP

Fab

How can Brownian Motion be observed in the Lab?

Follow this method: 1. Put some smoke in a brightly illuminated glass jar and observe the particles using a microscope. 2. The smoke particles appear as bright specks moving haphazardly from side to side, and up and down.

Explain how you can measure the specific latent heat of a solid or a liquid

For a solid: 1. Put a heating coil and equal masses of ice into two funnels above beakers 2. Turn on one heating coil for three minutes. Record the energy transferred in the three minutes. Dont turn on the other coil - use it to measure how much ice melts due to the ambient temperature of the room 3. After 3 minutes, measure the mass of water collected in the beakers. Subtract one from the other to get the mass of ice, m, that melted solely due to the presence of the heater 4. E = ml, so to find the specific latent heat of fusion for water just divide the energy supplied by the mass of ice that melted: L = E/m For a liquid: very similar experiment but boil the water in a distilling flask, condense the vapour given off and divide the energy transferred by the mass of condensed water collected.

In terms of circular motion, what is frequency? Give the various units

Frequency (f) is the number of complete revolutions per second. Units: (revs⁻¹, hertz (hz))

What is the difference in terms of energy between fusion and fission

Fusion gives you more energy per nucleon but fission generally gives you more energy per reaction

What does the area of a Charge against PD graph show? (Ensure you are familiar with the graphs on page 41)

Gradient = Charge/p.d. = capacitance

What are gravitational field lines?

Gravitational field lines (or lines or force) are arrows showing the direction of the force that masses would feel in a gravitational field.

(Equation (Learn) +) What is gravitational field strength? Give an equation to show it, units and the value on earth

Gravitational field strength, g, is the force per unit mass. Its value depends on where you are in the field. It can be calculated by the following formula: g = F/m where g is in newtons per kilogram (Nkg⁻¹) The value of g at the Earth's surface is approx 9.81 Nkg⁻¹ or ms

(Equation + ) Explain and derive the formula showing how an object's gravitational potential energy depends on its mass.

Gravitational potential is work done per unit mass, so the gravitational potential energy (E) of an object in a gravitational field is: E = mVg. Subbing in the formula for Vg, the gravitational potential energy of an object of mass m is: E = m(-GM/r) = -GMm/r where E is gravitational potential energy (J) and r is the distance form the centre of M to the centre of m (m)

(Equation) State, explain and give units for an equation referring to the attenuation of an X-ray signal

I = I₀e^-µx I₀ is initial intensity (usually measured in Wm⁻²) µ is the materials attenuation (absorption) coefficient (has units cm⁻¹) x is the distance from the surface (or depth) (measured in cm)

Define: Zeroth Law of Thermodyanamics

If body A and body B are both in thermal equilibrium with body C, then body A and body B must be in thermal equilibrium with each other.

Find the value of the time constant

If t = τ = CR is put in the equation for the charge, then Q = Q₀e⁻¹. Therefore, t = 0.37

(Formula +) Give a formula for working out the permittivity with multiple stations. (r) is subscript

If the plates have a material in between them instead of a vacuum, ε₀ is replaced with permittivity, ε where: ε = ε(r)ε₀ Where ε(r) is the relative permittivity (a ratio of the size of the electric field generated in a vacuum compared to if it will generated in a material).

(Equation +) Explain what would need to be assumed in terms of volume when calculating the mean nuclear density

If you are asked to estimate the mean nuclear density you might have to work out the volume of the nucleus from its radius - so just assume it is a sphere and use the formula for that: V = 4/3πr³

Explain what you can do when comparing absorption and emission spectra (See important diagrams on page 34)

If you compare the absorption and emission spectra of a particular gas, the black lines in the absorption spectrum match up to the bright lines in the emission spectrum

Use Newton's Laws to Explain the Pressure of an Ideal Gas

Imagine a cubic box containing N particles of an ideal gas each with a mass m 1. The particles of the gas are free to move around with constant, random motion. There are no forces of attraction between the particles, so according to Newton's 1st they continue to move with constant velocity until they collide with another particle or the box itself. 2. When a particle collides with a wall of the box, it exerts a force on the wall, and the wall exerts an equal and opposite force back (This is Newton's 3rd) 3. The size of the force exerted on the particle on the wall can be calculated using Newton's 2nd Law, which says that the force is equal to the rate of change of momentum. 4. For example, if particle Q is travelling directly towards wall A with velocity u, its momentum is mu. When it hits the wall, the force of the impact causes it to rebound in the opposite direction at the same speed. It's momentum is now -mu , which means the change in momentum is 2mu. 3. So, the force of a particle exerts is proportional to its mass and its velocity. The mass of a single gas particle is tiny (1 atom of helium is 6.6x10⁻²⁷ kg). So each particle can only exert a miniscule force. 6. But there are around millions of billions of particles in a box. The combined force is much bigger than the contribution from any individual particle. 7. Because there are so many particles in the box, a significant number will be colliding with each wall of the box at any given momentum, And because the particle's motion is random, the collisions will be spread all over he surface of each wall. The result is a steady, even force n all of the walls of the box - this is pressure.

Dark Matter

In Progress

What is key about SHM in terms of frequency, period and amplitude.

In SHM, the frequency and period are independent of the amplitude (they're constant for a given oscillation), so a pendulum clock will keep ticking in regular time intervals even if its swing becomes very small. This kind of oscillator is called an isochronous oscillator.

(Equation +) State and explain the equation for gravitational potential including units

In a radial field (like the Earth's), the equation for gravitational potential is: V(g) = - GM/r Where V(g) is gravitational potential (Jkg⁻¹), G is the gravitational constant, M is the mass of the object causing the gravitational field (kg), and r is the distance from the centre of the object (m).

What can be said about the graph of a system when it comes to damping?

In general, the more damped a system is, the flatter the graph of amplitude of oscillation against driving frequency.

Explain the circuit on the top of page 42

In this circuit, when the switch is flicked to the left, charge builds up on the plates of the capacitor. Electricity energy, provided by the battery is stored by the capacitor. 2. If the switch is flicked to the right, the energy stored on the plates will discharge through the bulb, converting electrical energy into light and heat.

Explain the effect of changing the volume with the equation pV = 1/3Nmc².

Increasing the volume of the container decreases the frequency of collisions because particles have further to travel in between collisions. This decreases the pressure

Define: Internal Energy

Internal energy is the sum of kinetic energy and potential energy of the particles within a system. (It is 0J as a gas, a large negative number when in a liquid and an even larger negative number when a solid)

Explain Annihilation Make sure you are happy with the diagram on page 67

It is the opposite of pair production 1. When a particle meets its antiparticle the result is annihilation 2. All the mass of the particle and the antiparticle gets converted to energy, in the form of a pair of photons. In ordinary matter antiparticles can only exist for a fraction of a second before this happens so you won't see many of them.

What conditions are needed for the Equation of State to give an accurate answer?

It works well (i.e., real gases approximate to an ideal gas) for gases at low pressures and fairly high temperatures.

State 4 factors that can make a nucleus unstable.

Its instability could be caused by: 1. Too many neutrons 2. Too many nucleons in total (it's too heavy) 3. Too few neutrons 4. Too much energy in the nucleus.

What does the centripetal force do?

Keep the object moving in a circle - remove the force and the object would fly off at a tangent.

How is linear velocity similar to angular velocity?

Linear velocity is defined as displacement/time, the angular velocity ω, is defined as angle/time

(Really?) What is Kelvin named after?

Lord Kelvin who first suggested it

What are medical tracers made out of? Give 2 specific examples

Medical tracers usually consist of a radioactive isotope: e.g technetium-99, or fluorine-18 - bound to a substance that is used by the body e.g. glucose or water,

Explain how hadrons decay. Are there any exceptions?

Most hadrons will eventually decay into other particles. The exception is protons - most physicists think that protons don't decay.

(Equation) From E=3/2kT, derive U = 3/2NkT

Multiplying by the number of gas particles, N, gives an equation for the internal energy, U, of an ideal gas: U = 3/2NkT

(Equation +) Form an equation using the number of undecayed nuclei remaining, N, the number originally present, N₀, the decay constant, λ and how much time has passed, t (seconds). How does this relate to a graph?

N = N₀e^-λt This is the equation of the line generated from the spreadsheet on page 73 (of N v t)

Give the Symbol, Relative Charge and Rest Mass (kg) of a Neutrino and it's relative Antiparticle (stating the name).

Neutrino: Symbol = ν Relative Charge = 0 Rest mass = 0 kg Antineutrino: Symbol = ν (with line overtop) Relative Charge = 0 Rest mass = 0 kg (Neutrinos are so tiny we assume that they have zero mass and zero charge)

Give the Symbol, Relative Charge and Rest Mass (kg) of a Neutron and it's relative Antiparticle (stating the name).

Neutron: Symbol = n Relative Charge = 0 Rest mass = 1.673 x 10⁻²⁷ kg Antineutron: Symbol = n (with line overtop) Relative Charge = 0 Rest mass = 1.673 x 10⁻²⁷ kg

For beta-plus radiation give the following information: 1. Ionising Power 2. Speed 3. Penetrating Power 4. If they are affected by magnetic field

None: Annihilated (destroyed) by electron - so virtually zero change

What is the helpful rule for working out forces on an object?

Number of things touching plus 1

Do Solar System pages previous

Ok

Do pages on Spectra of stars

Ok

Ensure you are happy with iterative modeling (page 44)

Ok

Ensure you are happy with the V-t Q-t, and I-t graphs on page 43 for charge and discharge

Ok

Make sure you are happy with escape velocity calculations such as that on page 25

Ok

Make sure you understand the experiment and graphs on page 20

Ok

Make sure you understand the graphs for different degrees of damping on page 21

Ok

Pages on Quarks below

Ok

See page 73 and ensure you are happy with mdoeling radioactive decay usung a spreadsheet

Ok

Make sure you are happy with the H-R graph on page 32, you know the different areas and the position of the sun relative to everything (1)

Ok Cool

State the cosmology principle

On a large scale the universe is homogenous (every part is the same as every other part) and isotropic (it looks the same in every direction), and in our Solar System to the rest of the universe.

Define: Astronomical Unit (AU)

One Astronomical Unit (AU) is defined as the mean distance between the Earth and the Sun.

Describe the kinetic model of a Liquid (see page 4 for diagrams)

Particles are constantly moving around and are free to move past one another but are attracted to each other

Describe the kinetic model of a Gas (see page 4 for diagrams)

Particles are free to move around with constant random motion. There are no forces of attraction between particles in an ideal gas

What are hadrons?

Particles that feel strong nuclear force

Describe the kinetic model of a Solid (see page 4 for diagrams)

Particles vibrate about fixed positions in regular lattice. They're held in position by strong forces of attraction

What do physicists picture in kinetic theory?

Picture gas particles moving at high speed in random directions

Explain how plastic deformation relates to damping

Plastic deformation of ductile materials reduces the amplitude of oscillations in the same way as damping. As the material changes shape, it absorbs energy, so the oscillation will become smaller.

How could you find CR

Plot a graph of lnQ against t while discharging - page 88-89 (p.d. or current would work to). The gradient of the line gives you -1/CR

(Equaiton +) Explain the basis behind and state Hubble's law. Explain each element and give units

Plotting the recessional velocity against distance shows that they're proportional i.e. the speed that galaxies move away from us depends on how far away they are . This suggests the universe is expanding and gives the rise to Hubble's Law: v = H₀d where v = recessional velocity in kms⁻¹, d = distance in Mpc and H₀ = Hubble's Constant in kms⁻¹Mpc⁻¹

Give the Symbol, Relative Charge and Rest Mass (kg) of a Proton and it's relative Antiparticle (stating the name).

Proton: Symbol = p Relative Charge = +1 Rest mass = 1.673 x 10⁻²⁷ kg Antiproton: Symbol = p (with line overtop) Relative Charge = -1 Rest mass = 1.673 x 10⁻²⁷ kg

(Equation) give the equation for the amount of charge left on the plates of a capacitor discharging from full Explain symbols and give units

Q = Q₀e^(-t/CR) Where Q₀ is the charge of the capacitor when it's fully charged (C) t is the time since discharging began (s) R is the resistance (Ω) C is the capacitance (F)

What is a quark?

Quarks are fundamental particles - the building blocks for hadrons like protons and neutrons

What is special about the way radioactive decay occurs? What information can we predict about decay?

Radioactive decay is random (p. 70), but for any radioactive sample, you can predict how many nuclei will decay in a given amount of time

Describe and explain when resonance happens (See graph on page 20 to make sure you understand)

Resonance occurs when the Driving Frequency = Natural Frequency 1. When the driving frequency approaches the natural frequency, the system gains more and more energy from the driving force and so vibrates with a rapidly increasing amplitude. 2. When this happens the system is resonating.

(Equation +) Describe and explain Charles's Law

Says that at a constant pressure, the volume, V of a gas is directly proportional to its absolute temperature, T Equation: V/T = Constant or Volume/Temperature = Constant

Explain what scientists are doing in terms of nuclear fusion research

Scientists are trying to develop fusion reactors so that we can develop nuclear electricity without the waste you get from fission reactions, but haven't yet succeeded in creating one that makes more electricity than it uses.

Make sure you are happy with the calculation on page 27 with Kepler's 3rd Law Calculations (and clever Ratio's)

See Book

Make sure you are fine with finding the specific heat capacity of a material.

See page 6

(Equation) Give the two equations for Centripetal force and explain their origin

Since F = ma (Newton's 2nd law the centripetal force is: 1. F = (mv²)/r or Force = (mass x linear velocitySquared)/radius 2. F = mω²r or Force = mass x angular velocitySquared x radius

What is special about the energy molecules in a gas have?

Some don't have much kinetic energy and move slowly. Others have loads of kinetic energy and whizz along. But most however are somewhere in between

Using the photo, explain Standard notation and it's role (See Pic and page 61)

Standard notation summarises the important informaton about an element's atomic structure: 1. The proton number or atomic number (Z) - there are size proton in a carbon atom (bottom number) 2. The nucleon number or mass number (A) (top number) 3. The symbol for the element (the letter)

Make your you are happy with the graph and calculation example on page 24 for gravitational potential

Sure

Define: Specific Heat Capcity

The Specific heat capacity (c) of a substance is the amount of energy needed to raise the temperature of 1 kg of the substance by 1 K (or 1°C).

Define: Capacitance

The amount of charge per unit volume stored by a capacitor

What is angular velocity?

The angle an object rotates through per second

Explain Critical Damping and Overdamping Give 2 applications of critical damping

The degree of damping can vary from light damping to overdamping: 1. Critical Damping reduce the amplitude (i.e. stops the system oscillating) in the shortest possible time 2. Car suspension systems and moving coil metres (which control the arm in analogue voltmeters and ammeters) are critically damped so that they son't oscillate but return to equilibrium as quickly as possible. 3. Systems with even heavier damping are overdamped. They take longer to return to the equilibrium position than a critically damped system

(Equation +) Describe and explain the SHM equations for displacement.

The displacement varies with the time according to one of the two equations, depending on where the object was when the timing was started. This determines whether the displacement-time graph is a cosine or sine wave. If you began timing when the displacement was at maximum x =Acos(ωf) If you began timing as the object passed through the midpoint x = Asin(ωf) (See notes in book for helpful tips with these) (These are solutions of the equation a = -ω²x)

(Equation) State an explain the equation used relating energies of photons and the difference in energies between two levels

The energy carried by each photon is equal to the difference in energies between two levels. It's given by the equation: ∆E = hf = hc/λ Where h = Planck's constant: 6.63 x10⁻³⁴ Js⁻¹, c is the speed of light, 3.00 x10⁸ ms⁻¹, λ is the photon's wavelength and f is the photon's frequency

Define: Binding Energy

The energy needed to separate all of the nucleons in a nucleus is called the binding energy (measured in MeV), and is equivalent to the mass defect

Explain speed with the equation pV = 1/3Nmc².

The faster the particles are going when they hit the walls, the greater the change in momentum and force exerted.

(Equation+) State and explain Coulomb's law.

The force of attraction or repulsion between two point charges: F = Qq/(4πε₀r²) ε₀ ("epsilon-nought") is the permittivity of free space Q and q are the charges r is the distance between Q and q

Define: Half Life (Note, slash is subscript)

The half life (t₁/₂) of an isotope is the average time it takes for the number of undecayed nuclei to halve

What is the intensity of the X-ray beam?

The intensity of the X-ray beam is the power (energy per second) per unit area passing through a surface (at right angles).

What is special about the energy required, the time taken to change state and the mass?

The larger the mass of the substance, the more energy it takes to change its state.

Explain, giving a formula, how Newton's Law of Gravitation is an Inverse Square Law

The law of gravitation is an inverse square law so: F ∝ 1/r² 1. If the distance r between the masses increases then the force F will decrease 2. If the distance doubles then the force will be one quarter the strength of the original force

(Equation +) Describe and explain Stefan's Law

The luminosity is proportional to the forth power of the star's temperature and directly proportional to its surface area: L = 4πr²σT⁴ Where L is the luminosity of the star (in W), r is the radius (in m), T is its surface temperature (in K) and σ is the Stefan constant (5.67 x10⁻⁸ Wm⁻²K⁻⁴)

Explain what the luminosity of a star is

The luminosity of a star is the total energy is emits per second i.e. its power output

Explain mass with the equation pV = 1/3Nmc².

The mass, m, of the particles - according to Newtons 2nd Law, force is proportional to mass, so heavier particles will exert a greater force.

Explain the effect of changing the number of particles with the equation pV = 1/3Nmc².

The number of particles, N, - increasing the number of particles increases the frequency of collisions between the particles and the container, so increases the total force exerted by all the collisions

Explain how energy changes happen between particles

The particles of a gas collide constantly with each other. Some of these are 'head on' (particles moving in opposite directions) while others will be 'shunts from behind' (particles moving in the same direction). 1. As a result of the collisions, energy will be transferred between particles 2. Some particles will gain speed in a collision and others will slow down 3. Between collisions, the particles will travel at a constant speed 4. Although the energy of an individual particle changes at each collision, the collisions don't alter the total energy of the system.

State Kepler's Third Law See diagram on page 27

The period of the orbit and the mean distance between the Sun and the planet are related by Kepler's third law: T² ∝ r³

In terms of circular motion, what is the period? Give the various units

The period, T, is the time taken for a complete revolution (in seconds). Units: Seconds (s)

How is the output from a radioacive tracer recorded?

The radiation emitted is recoreded e.g. by gamma camera of PET scanner (see extra cards) and an aimage of inside the patient is produced

Explain how radioactive isotopes can be used to Date Objects

The radioactive isotope carbon-14 is used in radioactive dating 1. Living plants take in carbon dioxide form the atmosphere as part of photosynthesis, including the radioactive isotope carbon-14. Animals then take this carbon-14 in the way they eat the plants. All living things contain the same percentage of carbon-14. 2. When they die the activity of the carbon-14 in the plant starts to fall with a half-life of around 5730 years. 3. Archaeological finds made from once-living material (like wood) can be tested to find the current amount of carbon-14 in them. THis can be used to calculate how long the material has been dead for - i.e. how old it is.

Define: Specific latent heat

The specific latent heat (L) of fusion or vaporisation is the quantity of thermal energy required to change the state of 1 kg of a substance

Explain how capacitors can be used in back-up power supplies

These often use lots of large capacitors that can release charge for a short period. If the power supply goes off e.g. for keeping computer systems running if there's a brief power outage

Describe and explain what happens when objects travel in circles

They are accelerating since their velocity is changing 1. A car for example can be going at a constant speed, its velocity is changing since its direction is changing. 2. Since acceleration is defined as the rate in change of velocity, the car is accelerating even though it isn't going an faster. 3. This acceleration is called the centripetal action and is always directed towards the centre of the circle

Explain the life cycle of massive stars (one with a high mass).

They have a shorter life and a more dramatic death: 1. Stars with a large mass have a lot of fuel, but they use it up more quickly and don't spend so long as main sequence stars. 2. When they are red giants the 'core burning to shell burning' process can continue beyond the fusion of helium, building up layers in a n onion-like structure to become Super Red Giants (or red super giants). 3. For really massive stars, fusion can go all the way up to iron. Nuclear fusion beyond iron is energetically favourable (see other cards) so once an iron core is formed then very quickly it is the end of the star. 4. When the core of the tar runs out of fuel, it starts to contract, forming a white dwarf core. 5. If the star's core is larger than the Chandrasekhar limit, electron degeneracy pressure cannot stop the core contracting. This happens when the mass of the core is 1.4 times the mass of the sun. The core of the star continued to contract and as it does, the outer layers fall in and rebound off the core, setting up huge shock waves. These shock waves cause the star to explode cataclysmically in a Supernova, leaving behind a Neutron star (or when they are particularly massive) a Black Hole. Light form a supernova can briefly outshine an entire galaxy.

Explain what E = 3/2kT shows

This equation shows that the average kinetic energy and internal energy are both directly proportional to the absolute temperature - a rise in absolute temperature will cause an increase in the kinetic energy of the particles, meaning a rise in the internal energy.

What is the time constant?

Time Constant (τ) = CR

(Equation) Give the equation for the mean nuclear density and units of density

To calculate the mean density of a nucleus, you need to know the mass and volume of the nucleus and the equation for density: ρ = m/v where ρ is measured in kgm⁻³

What is the circuit symbol for a capacitor

Two Parallel Lines (See Photo)

Briefly Explain the process of nuclear fusion

Two light nuclei can combine to create a larger nucleus.

(Equation) Give the formula for electric potential in a radial field around a point charge. Give units and explain terms

V = Q/(4πε₀r) Where V is the electric potential (V), Q is the size of the point charge (C) and r is the distance from the point charge (m).

(Equation +) Describe and explain the SHM equations for velocity (for normal and max).

Velocity is a vector quantity, so the direction of motion matters as well as the speed - that's why there's a ± sign. Velocity v = ±ω√(A²-x²) (In Formula Booklet) Max Velocity vmax = ωA (When v = vmax, x = 0) (Not in Formula Booklet - LEARN) (This is based on v = rω and is deffo a get out of jail formula)

Explain the velocity graph for SHM on page 16

Velocity, v, is the gradient of the displacement-time graph. It is a quarter of a cycle in front of the displacement (a phase difference of π/2) and has a maximum value of ωA.

What is the purpose of a controlled nuclear reactor?

We can harness the energy released during nuclear fission reactions in a nuclear reactor, but it's important that these reactions are very carefully controlled.

Explain how antiparticles were predicted before they were discovered Explain the difference between a position and an electron

When Paul Dirac wrote down an equation obeyed by electrons, he found a kind of mirror image solution 1. It predicted the existence of a particle like the electron but with an opposite electric charge - the positron 2. The positron turned up later in a cosmic ray experiment. Positrons have an identical mass to electrons but they carry a positive charge

Explain how capacitors can be used in Smoothing out P.D.

When converting an a.c. power supply to d.c. power, capacitors charge up during the peaks and discharge during the troughs, helping to maintain a constant output.

Explain ionising radiation

When radiation hits an atom, it can knock off elections creating an ion - so radioactive emissions are also known as ionising radiation.

What does the specific heat capacity effect?

When you heat something, the amount of energy needed to raise its temperature depends on its specific heat capacity.

Explain how capacitors can be used in Flash Photography

When you take a picture, the capacitor has to discharge really quickly to give a short pules of high current to create a brief, bright flash.

Explain in detail how X-rays are produced. (See diagram on page 80)

X-ray tubes are an electrical circuit, with a cathode (where electrons are emitted) and anode (the target metal) 1. At the cathode, electrons are emitted (boiled off) by the hot filament 2. This filament is heated by passing a current through it. This current is not the same as that going through the entire X-ray tube. 3. The cathode is usually in a cup shape, to focus the beam of electrons onto the target metal. 4. The target metal (tungsten - used due to high melting point etc.) acts as the anode of the circuit, and the high potential difference across the tube (tube voltage) causes the electrons to accelerate towards it. 5. When the electrons smash into the tungsten anode they decelerate and some of their kinetic energy is converted into electromagnetic energy in the form of X-ray photons. The tungsten anode emits a continuous spectrum of X-ray radiation

(Equation +) Explain how you can calculate the minimum energy a photon must have under pair production and the maximum wavelength/frequency

You can calculate the minimum energy Eᵧ, using ∆E = ∆mc²: 1. The minimum energy a photon must have to under pair Production (Eᵧ) must be equal to the energy (at rest) of the particles produced. 2. A particle and its antiparticle have the same rest mass (m), which means that Eᵧ = 2mc² 3. You can go further and find the maximum wavelength or minimum frequency of the photon using the equation for the energy of a photon: Eᵧ = hc/λ = hf 4. Just put these two equations for Eᵧ together and rearrange to find λ or f.

Explain in brief how you can find the capacitance of a capacitance from the the electric potential

You can use the formula for electric potential of a radial field and the fact that Q = CV (page 40) for capacitors to derive an expression for the capacitance of an isolated charged sphere, assuming the charge is evenly distributed.

(Equation) State Wien's Displacement Law (See example Q on page 35)

You can use this to estimate a star's peak surface temperature, when T is in kelvins. λ(max) ∝ 1/T

Explain what an absorption spectrum is and how it works

You get a line absorption spectrum when light wight a continuous spectrum of energy (white light) passes through a cool gas: 1. At low temperatures, most of the electrons in gas atoms will be in their ground states 2. Photons of the correct wavelength are absorbed by the electrons to excite them to higher energy levels 3. These wavelengths are missing from the continuous spectrim when it comes out on the other side 4. You will see a continuous spectrum with black lines in it corresponding to the absorbed wavelengths.

Explain how particles in Electric Fields can act as projectiles

You'll probably remember that projectiles move through a uniform gravitational field along a curved path (you met this in year 1 and A-level). 1. A particle of charged Q will experience a constant force, given by F = EQ, acting parallel to the electric field lines. 2. If the particle is positively charged then the force in the same direction as the field lines, if it's negatively charged (e.g. an electron), the force is in the opposite direction to the field lines. 3. The work done on the particle y the force (W = fd) increase its kinetic energy and causes it to accelerate at a constant rate in the direction of the force (Newton's second law). 4. If the particle's velocity has a component at right angles to the field lines, this component will remain unchanged and the velocity in this direction will be uniform. That's Newton's first law. 5. The combined effect of constant acceleration and constant velocity at right angles to one another is a curved path.

What is special about zero kelvin?

Zero kelvin is the lowest possible temperature and is called absolute zero.

What are relative charges relative to?

e = 1.60 x 10⁻¹⁹

(Equation) Give the equation that links frequency and time period

f = 1/T or Frequency = 1/time period

Give the equation relating the spring constant, mass and angular frequency

k = -ω²m

(Useful Extra Equation) Give a formula relating moles, mass and molar mass (g/mol) (relative formula mass in grams)

n = M/Mr

(Equation) Give the equation relating pressure, number of particles, their mass and speed. Give all the various units

pV = 1/3Nmc² (c² should have a bar over it - see textbook) p = Pressure (Pa) V = Volume (m³) N = number of particles m = mass (kg) c(bar)² = mean square speed - it represents the mean of the squared speed of all the particles

(Equation) Give the formula for escape velocity and give the units

v = √(2GM/r) Units of ms⁻¹

Explain the different elements of the equation: v = √(GM/r) and give units for each

v is orbital speed in ms⁻¹ G is gravitational constant 6.67x10⁻¹¹ in Nm²kg⁻² M is the mass of the object being orbited (the larger one in the centre) (kg) r is the distance form the centre of the object being orbited to the centre of the orbiting satellite (m)

(Equation) Give the equation relating linear velocity and angular velocity What are the units?

v=rω or linear velocity = radius * angular velocity Units: ms⁻¹

State (and explain) what happens in the alpha decay of ²³⁸₉₂U

²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂α (238 = 234 + 4 so the nucleon numbers balance) (92 = 90 + 2 so proton numbers are balanced and charge is conserved)

State (and explain) what happens in the Beta-minus decay of ¹⁸⁸₇₅Re

¹⁸⁸₇₅Re → ¹⁸⁸₇₆Os + ⁰₋₁β + ⁰₀v (v has line over top) (188 = 188 + 0 + 0 - nucleon numbers balance) (75 = 76 - 1 + 0 - proton numbers balance charge is conserved)

State (and explain) what happens in the Beta-plus decay of ¹⁸₉F

¹⁸₉F → ¹⁸₈O + ⁰₁β + ⁰₀v (line over the top of B, plus on one on the bottom of the B) (18 = 18 + 0 + 0 so nucleon numbers balance) (9 = 8 + 1 + 0 so proton numbers balance and charge is conserved)

Give a formula relating work done, mass and gravitational potential

ΔW = mΔVg Where ΔW is the work done (J), m is the mass of the object (kg) and ΔV is the gravitational potential difference (Jkg⁻¹)

(Equation) Give the equation for calculating an isotope's half-life mathematically Give Units (Slash is subscript)

λt₁/₂ = ln2 Where ln is the natural log (see page 8), λ is the decay constant in s⁻¹ and t₁/₂ is the half life in seconds

Explain how you can find τ experimentally

τ can be found experimentally by using a voltmeter and timing how long it takes a discharging capacitor to reach 37% of its starting potential difference

(Equation) Give the equation linking angular velocity, angle and time What are the units? What kind of unit is this?

ω = θ/t or Angular velocity = angle/time Units: rad s⁻¹ It is a vector quantity - it has a size and a direction.

(Equation+) Describe and state 2 equations for SHM motion - and give units

ω is the angular frequency of the oscillation (in rads⁻¹). It is the magnitude of the vector quantity angular velocity: ω = 2π/T and ω = 2πf (as before) (T is the time taken for one oscillation and f is the number of oscillations per second)

(Equation) Give the equation linking energy, mass and the speed of light and explain each individual part and units

∆E = ∆mc² ∆E = the energy released in J ∆m = the mass defect in kg c = the speed of light in a vacuum

(Equation +) Give a formula for Ultrasound Waves and the Doppler Effect Explain the different elements of it

∆f/f = 2vcosθ/c or v = c∆f/2fcosθ Where f is the initial frequency, ∆f is the change in frequency v is the velocity o the moving cell c is the speed of sound in that medium θ is the angle between the ultrasound receiver and the direction in which the cell is moving.

(Equation +) Give a formula to determine the amount of red or blue shift Explain the individual elements

∆λ/λ = ∆f/f = v/c Where ∆λ is the difference between the observed and emitted wavelengths, λ is the emitted wavelength Where ∆f is the difference between the observed and emitted frequency, λ is the emitted frequency v is the velocity of the source in the observer's direction and c is the speed of light