Astronomy Quiz 5

How do you measure the energy of a wave?

Energy = constant X frequency (energy = dependent upon frequency) constant = planck's constant = h

What 3 fundamental properties do line spectra posses that we can measure?

-1) Location (wavelength or frequency) -2) Intensity (relative to continuum and each other) -3) Width

What is an electromagnetic field and what produces one?

-Charge <-> electric field -Moving charge <-> magnetic field -Time varying E-field <-> time varying B-field

What is Planck's Law?

-Describes the overall shape of the BB curve •It has a central peak and falls off sharply on both sides of the peak, but is not symmetric

Explain the uncertainty principle

-Higher frequency = higher energy -If there's multiple waves then there will be multiple energies that affect each other -If we can say exactly how much energy a wave has then we don't know where the wave is, it is "infinite", no particular place that the wave exists -If there are multiple waves in a wave packet then we can better tell where the wave is than if theres only a singular wave -When multiple waves are added together, their energy is added together and their location get's zero'd in on but we can no longer tell what the frequency of the wave is

In thermal radiation what is the idealized radiator called and what does it do?

-Idealized radiator is called a Black Body -Completely absorbs and emits light at all wavelengths

The electrons orbiting atomic nuclei are found at various distances from the nucleus, determined by the standing wave criteria of de Broglie. How are these distances determined?

-The distance is directly related to an energy level. -Just as your energy increases as you climb higher up a ladder. The 'higher' the electron's orbit, the more energy it has.

What is the Stefan-Boltzmann law?

-The energy radiated per unit area increases with (4th power of) the temperature T => Brightness (Stefan-Boltzmann) -If we know Radius => Luminosity => Distance -Or if we know D => L => R of source

What is Wien's Law?

-The frequency of the maximum of the radiation goes up as T increases -Equivalently, we can say the wavelength of the maximum of the radiation decreases as T increases Color => Temperature (effective)

What happens when an atom absorbs energy?

-When this happens, an electron moves from a lower orbit to the next higher orbit. -The atom has increased its energy. -However, as fast as it absorbed this energy it will release it, thus radiating a spectral line.

what is one discrete wiggle in the electromagnetic field?

-photon or particle -on the other hand if there is a continuous wiggle that would be described as a wave.

•What do we observe when electromagnetic radiation (light) hits a piece of metal? (the photo-electric effect occurs)

1) negative particles are emitted 2) They are forcibly ejected by the light 3) The emitted particles are electrons 4) Number emitted proportional to intensity 5) Kinetic energy of electrons is independent of the intensity of the light 6) Only light above certain frequencies kick off electrons (threshold) 7) As frequency of light increases above threshold the energy of the electrons increases.

Two fundamental observable qualities of light:

1)Brightness 2)Color

Describe the three types of spectra

1)Continuous: Solids, Liquids, and gases produce this thermal "glow"; this is a characteristic of a dense gas 2)Absorption line: Dark line spectra when a rarified gas is in front of a source of continuous light 3)Emission line:Bright line spectra when a rarified gas is lit by a continuum but seen against a dark background.

What does the wave packet of electrons mean for electron's orbits?

1)It means they have no orbital path! 2)The orbits are "wave resonances", or "standing waves" like the waves on a guitar string—Louis de Broglie 3)Each orbit must contain only an integer number of electron wavelengths, so only certain orbits (energy levels) are allowed. Shorter wavelengths<->higher momenta, and hence energy, of the electrons. 4)Now we can understand the "fingerprints" or spectral line signatures of each atom. They are the photons emitted or absorbed only when their energy (given by the Einstein frequency condition) corresponds to the energy difference between allowed orbits

What is a wave? Use the terms wavelength and frequency in your definition.

A wave is characterized by the cyclic occurrences of crests and troughs. Wavelength is defined as the distance between two consecutive troughs or two crests and the Frequency is defined as the number of cycles that pass through a point per second.

What is meant by "reflecting" and "refracting" telescopes?

A reflecting telescope uses a mirror as the primary light collector, reflecting light into the spectrometer and detector. A refractor uses lenses to focus light.

24. Suppose a photon approaches a hydrogen atom in its ground state. The photons energy is less than the energy between the ground state and the next orbit above the ground state. What happens to the photon? A. It passes through the atom, as if the atom were not there. B. It is absorbed and re-emitted in the same direction. C. It ionizes the atom, and the electron escapes. D. It is absorbed and re-emitted in a different (random) direction. E. The electron jumps up to the next orbit, then immediately falls back to the ground state.

A. It passes through the atom, as if the atom were not there. Note:The photon does not have enough energy to excite the electron from the ground state to the first state, therefore it cannot do anything to the orbit of the electron.

11. If a star is moving toward us rapidly and we observe its spectrum, we expect the absorption lines to appear______than if the star were at rest. A. at shorter wavelengths B. in eclipse C. in emission D. at longer wavelengths E. None of the above.

A. at shorter wavelengths This is due to the Doppler effect. Since the star is moving toward us, the lines are shifted to shorter wavelengths. If the star were moving away from us they would be shifted to longer wavelengths.

7. The alternating light and dark lines you see when you form a narrow slit with your fingers and look at a light source is fundamental proof that light, at least sometimes, behaves like a wave. This alternating light and dark pattern is caused by: A. diffraction and interference. B. reflection and transmission. C. refraction and reflection. D. the particle nature of light. E. None of the above.

A. diffraction and interference. In basic terms, diffraction occurs when a wave encounters an obstacle or a slit that is comparable in size to its wavelength, whereas interference is the phenomenon where waves meet each other and combine additively or substractively.

13. The speed of light in a vacuum is constant. This means that if we know the wavelength of a photon, we also know the. A. frequency B. Facebook status C. mass D. origin E. polarization

A. frequency This is because the speed of light, c, is the frequency of light times the wavelength of that light:c = wavelength×frequency.

Which type of wave has a longer wavelength: AM radio waves (with frequencies in the kilohertz range) or FM radio waves (with frequencies in the megahertz range)? Explain.

AM radio waves have a lower frequency. According to the wave equation, waves with a lower frequency must have a larger (longer) wavelength. To put it another way, frequency is inversely proportional to wavelength.

Explain how electrons use light energy to move among energy levels within an atom.

An atom can absorb energy(photons), which raises it to a higher energy level, this causes an electron's movement to a larger orbit and is called excitation.

What emits thermal radiation? (light)

Anything with a temperature above absolute zero will emit thermal radiation even if it's not visible (infrared radiation) even the coldest objects in the universe are emitting radiation (bc they are not 0 K)

What trend do black body spectra show when heated to different temperatures?

As black body temperature increases the maximum wavelength intensity shifts to shorter wavelengths (higher frequencies) and vice versa, this corresponds with the observations made in Planck's Law.

Explain why astronomers use the term "blueshifted" for objects moving toward us and "redshifted" for objects moving away from us.

As wavelength gets shorter, they shift toward the blue end of the spectrum: astronomers call this a blueshift. When the wavelength gets longer, we call the change in colors a redshift.

Explain why astronomers long ago believed that space must be filled with some kind of substance (the "aether") instead of the vacuum we know it is today.

Astronomers thought that light, like other waves, needed some medium through which to propagate (like sound moves through air, water, or solids), and since we get light from distant planets and stars, they thought space must therefore be filled with a substance like the aether to be a medium for traveling light waves. We now know light does not require a medium to propagate.

25. We learned that matter has both particle and wave properties. Why don't we see obvious wave phenomena occurring in our everyday interactions with material? A. Everyday objects are always in the presence of an observer. B. Everyday objects have wavelengths that are too short to have noticeable wave-like behavior. C. Only subatomic particles have wave properties. D. Matter only acts like a wave during careful laboratory experiments. E. None of the above.

B. Everyday objects have wavelengths that are too short to have noticeable wave-like behavior. Quantum mechanics is the most correct description of the entire universe that we have discovered to date. The wave-particle duality could theoretically be observed for all objects, but in practice it's impossible for large objects like humans or baseballs.

9. Which of the following descriptions of light is incorrect? A. Visible light is a small part of the electromagnetic spectrum. B. Light cannot carry energy. C. The speed of light in a vacuum is constant. D. Light is an electromagnetic wave. E. Light obeys the inverse square law.

B. Light cannot carry energy. Light carries energy, which is why it takes energy to power a light bulb. It obeys the inverse square law, because the amount of energy spreads out over an area. Light is an electromagnetic wave, of which visible light is the small portion of the electromagnetic spectrum that is visible to the human eye. The speed of light in a vacuum is 186,282 miles per second (299,792 kilometers per second). From our current understanding of physics nothing can travel faster than light.

16. Ripples are to a pond as_________is to__________. A. a Ruffle; Frito-Lay B. a photon; the electromagnetic field C. gravity; mass D. gravity; acceleration E. sound; the electromagnetic field

B. a photon; the electromagnetic field Photons, or light, are ripples in an electromagnetic field.

14. When an electron makes a downward transition to a lower orbit in an atom it: A. gains energy. B. emits a photon. C. absorbs a photon. D. B and A E. None of the above.

B. emits a photon. This is an example of conservation of energy. The electron loses energy by making a moving from a high energy orbit to a lower energy orbit (i.e. a downward transition), consequentially emitting a photon. These photons have an energy equal to the difference between the energies of the electron orbits.

4. Einstein and the photoelectric effect tells us that the energy of a photon is directly proportional to the________of the photon? A. intensity B. frequency C. speed D. amplitude E. None of the above.

B. frequency Energy = constant×frequency. The photoelectric effect is the process where electrons are liberated from the surface of a metal by light. Light needs a sufficient amount of energy in order to knock an electron loose. When this is done in an electric field, the amount of energy can be measured, demonstrating the relationship between wavelength or frequency and energy.

18. The "chorus line" demonstration in class, where students stood in front and demonstrated waves moving through a medium, illustrates that A. very few astronomy students will make it on Broadway. B. the speed of light decreases in a denser material. C. the speed of light increases in a denser material. D. the speed of light is independent of the density of the material. E. the speed of sound decreases in a less dense material.

B. the speed of light decreases in a denser material. Light travels more slowly through a denser medium. As the density of a material increases, and the speed of light in that material decreases. Recall how the wave travelled faster when half of the people(the medium) sat down.

Why is it difficult to observe at infrared wavelengths? What do astronomers do to address this difficulty?

Both telescopes and Earth itself emit a lot of infrared radiation that is difficult to separate from the radiation coming from astronomical sources. To solve the problem, astronomers either shield the detector from its surroundings by cooling it or they make infrared observations from high in the atmosphere or from space.

Is light a particleor awave or both?

Both, as so is everything else in the universe Sometimes they behave as particles, and sometimes as a waves.

1. According to the inverse square law of light, how will the apparent brightness of an object change if its distance to us quadruples? A. Its apparent brightness will decrease by a factor of 32. B. Its apparent brightness will decrease by a factor of 2. C. Its apparent brightness will decrease by a factor of 16. D. Its apparent brightness will decrease by a factor of 4. E. Its apparent brightness will decrease by a factor of 8.

C. Its apparent brightness will decrease by a factor of 16.

6. In order to observe fainter objects we need to increase the_______of a telescope. Seeing fainter objects allows us to see. A. magnification; finer details B. refracting power; life on other planets C. aperture; farther back in time D. focal length; hotter stars E. None of the above.

C. aperture; farther back in time The key characteristic of a telescope is the aperture of the main mirror or lens. The larger the aperture, the more light you can gather, and the fainter the objects you can see or photograph.

3. Light and electrons both A. travel at the speed of light. B. contribute to the dark energy content of the universe through their interaction with other matter. C. behave like waves and particles. D. have a wide range of possible colors.

C. behave like waves and particles. Light does travel at the speed of light, but electrons must travel slower than light because they have mass. Color refers to the wavelength of light; while electrons do sometimes act as a wave, they don't have a wavelength in the same way that light does. Dark energy is neither light nor matter, so it does not interact with light or electrons (more on this later in class). Both electrons and light some times act as particles and sometimes act as waves.

15. If we refer to an object as a "blackbody," we imply that: A. it is a nearly perfect reflector of radiation. B. it absorbs light in the visual and reflects light in the infrared. C. it is a nearly perfect absorber and emitter of radiation. D. it is a completely cold object. E. it absorbs all radiation incident upon it and does not reradiate at any wavelength.

C. it is a nearly perfect absorber and emitter of radiation. This is the definition of a blackbody: an ideal radiator and absorber of energy at all electromagnetic wavelengths. The term comes from the fact that a cold blackbody appears visually black. The energy emitted by a blackbody is called blackbody radiation. In real life black bodies don't exist, but objects like stars and lamps are close enough to be blackbodies that we can treat them as such.

22. Heisenberg's uncertainty principle says that the uncertainty in_________increases when our uncertainty in___________decreases. A. distance; luminosity B. wavelength; frequency C. position; momentum (speed or velocity) D. position; intensity E. None of the above.

C. position; momentum (speed or velocity) n quantum mechanics, Heisenberg's uncertainty principle is a fundamental limit to the precision with which certain pairs of physical properties of a particle, can be known. An example of this is position and speed - if you know the position of the particle exactly, then you can't know the speed of the particle at all. In general, the product of two related quantities is a constant.

23. The frequency of light is essentially: A. the frequency with which air is vibrating into your eye. B. the amplitude of distorted space-time around an atom. C. the frequency with which a charge, such as an electron, is wiggled. D. All of the above. E. None of the above.

C. the frequency with which a charge, such as an electron, is wiggled. You can remember this by remembering that electromagnetic radiation has electro(n) in it.Wiggling an electron will create waves in the electromagnetic field. These waves are "seen" as light.Light is measured by its wavelength (in nanometers) or frequency (in Hertz). One wavelength equals the distance between two successive crests or troughs of a wave. Frequency (Hertz) is the number of crests or troughs of a wave that passes a given point each second.

21. What is the proper order of colors in visible light, in order of increasing wavelength? A. violet, red, orange, yellow, indigo, green, blue B. yellow, orange, red, green, blue, violet, indigo C. violet, indigo, blue, green, yellow, orange, red D. red, orange, yellow, green, blue, indigo, violet E. None of the above.

C. violet, indigo, blue, green, yellow, orange, red Red light has the longest wavelength (about 700 nm) within the visible range, blue light has the shortest (about 400 nm). The order is the same as that in a rainbow in between red and blue.

What aspect of a wave is color related to?

Color is related to frequency -High frequency = bluer light-faster wiggle -Low frequency = redder light-slower wiggle -high temperature requires higher energy which will result in higher frequency

What is a wave packet?

Condensed area of waves -Can take different forms -The waves interfere with each other (called interference) to form the shape of the wave packet

10. The reason we only observe certain wavelengths of light in an emission line spectrum is that A. an electron has wave properties, so it can only exist in orbits where an integral number of its wavelengths fit. B. only certain energy levels are possible for an electron orbiting a nucleus. C. light exists in discreet lumps, or quanta, each with a certain energy. D. All of the above. E. None of the above.

D. All of the above. Check Lecture Notes 14: Light and Matter Theory, page 14-16.

8. How do clouds interact with light? A. Emission. B. Absorption. C. Scattering. D. Transmission. E. All of the above.

E. All of the above. Most of these are best seen during the day: if the clouds are thin enough, you can see the Sun through them, so the clouds must transmit light. They make the Sun appear dimmer, though, so they also absorb and scatter light. The light becomes more diffuse, and you can see light from clouds that are near the horizon, so they scatter light. Clouds are generally blackbodies, so they emit light, though that light is in the infrared so it can't be seen by eye. Clouds also reflect light.

20. What is error in a scientific experiment? A. Imperfections introduced into the experiment because it is being performed by people instead of robots. B. A mistake that the researcher made when performing the experiment. C. A problem in the methodology devised as part of the experiment. D. The natural uncertainty that occurs in every measurement and phenomenon. E. All of the above.

D. The natural uncertainty that occurs in every measurement and phenomenon. Error in the context of a scientific experiment refers to the uncertainty in the measurements and the phenomena. The Heisenberg uncertainty principle tells us that no one quantity can be perfectly known — this is true of any event as well as measurements of that event. The best possible measurement of any event will always have uncertainty in the result. Scientific experiments are designed to minimize the uncertainty within the limitations of the equipment and methods used in the experiment.

2. The gas with the simplest emission line spectrum (demonstrated in class) is A. the incandescent bulb. B. helium. C. carbon dioxide. D. hydrogen. E. None of the above.

D. hydrogen. Hydrogen has only one electron, so the orbital structure is very simple.

12. The atom is: A. mostly solid space. B. sort of like a pudding. C. indestructible. D. mostly empty space.

D. mostly empty space. Physicist Ernest Rutherford established the nuclear theory of the atom with his gold-foil experiment. When he shot a beam of alpha particles at a sheet of gold foil, a few of the particles were deflected. He concluded that a tiny, dense nucleus was causing the deflections. The space between atoms is maintained by attractive and repulsive forces between the electrons in each atom and the positively charged nuclei of each atom.

17. Waves in a guitar string are an example of waves________. Sound waves in air are____________waves. A. longitudinal; longitudinal B. transverse; transverse C. longitudinal; transverse D. transverse; longitudinal E. None of the above.

D. transverse; longitudinal Transverse waves involve the medium moving up-and-down or side-to-side, like a guitar string, rope, slinky, or surface waves on a pond. Longitudinal waves involve the compression and rarefaction of a medium. Sound, and a slinky that is pulled tight then released are examples of longitudinal waves.

19. If you are star-gazing on a clear night and notice two stars, one of which appears bluish and the other reddish, what could you conclude about the relative characteristics of the two stars? A. The red star has a higher surface temperature than the blue star. B. The blue star radiates more energy per unit area than the red star. C. The blue star has a higher surface temperature than the red star. D. The red star radiates more energy per unit area than the blue star. E. C and B

E. C and B Thermal radiation has a color that is dependent on the temperature. Hotter objects are more blue, cooler objects are more red. Bluer light is higher frequency, or shorter wavelength, and carries more energy than red light. The energy per unit area (or flux) is higher when the same area is emitting bluer light than when it is emitting redder light.

5. Which of the following is not a form of electromagnetic radiation? A. Gamma-rays B. Radio waves C. Sunlight D. X-rays E. Electrons

E. Electrons X-rays, gamma-rays, and radio waves are all forms of electromagnetic radiation. X-rays have a wavelength ranging from 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertzto 30 exahertz (3×1016Hz to 3×1019Hz). Gamma rays, orγ-rays (γis the Greek letter gamma, are high energy electromagnetic radiation with wavelengths shorter than, or frequencies higher than, x-rays. Gamma rays are often associated with radioactivity. Radio waves are low energy electromagnetic radiation with frequencies as less than 300 GHz. Sunlight consists of all of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. Electrons are normal matter are are not electromagnetic radiation, through they do interact with electromagnetic radiation because of their negative charge.

Explain how we use spectral absorption and emission lines to determine the composition of a gas

Each particular gas can absorb or emit only certain wavelengths of the light peculiar to that gas. It's the precise pattern of wavelengths that makes the signature of each element unique.

What is Einstein's frequency condition?

Einstein's frequency condition: E = hf •This says the light comes in wave-packets, or particle-like "quanta" and that the energy of these quanta is a constant, h, times the frequency, f, of the quanta. These quanta are called photons.

What is the Medium for Light?

Electromagnetic field

Explain how emission lines and absorption lines are formed. In what sorts of cosmic objects would you expect to see each?

Emission lines are formed when electrons jump to lower energy levels and emit photons. Absorption lines are formed when electrons jump to higher energy levels by absorbing photons

Which is more dangerous to living things, gamma rays or X-rays? Explain.

Generally the radiations like X rays, Gamma rays and UV rays, all are harmful and dangerous as they cause harm to living creatures. Gamma rays are a lot more dangerous and hazardous to human health than X-rays. Moreover gamma rays are the highly penetrating and highly energetic ionizing radiation. On prolonged exposure to living beings they can cause cancer.

What determines whether we see absorption or emission lines?

Geometry

Give examples of transverse waves:

Guitar string, rope, surface waves on a pond, slinky

What are the three isotopes of hydrogen, and how do they differ?

H1 (Hydrogen 0Neutrons) H2 (deuterium, 1Neutrons) H3 (tritium, 2Neutrons)

Explain why hotter objects tend to radiate more energetic photons compared to cooler objects.

Higher-energy photons correspond to higher-frequency waves (which have a shorter wavelength); lower-energy photons are waves of lower frequency. when electrons go from lower levels to higher ones, they must absorb a photon of just the right energy, and when they go from higher levels to lower ones, they give off a photon of just the right energy.

Explain the difference between radiation as it is used in most everyday language and radiation as it is used in an astronomical context.

In everyday usage, the term radiation can refer to highly energetic photons or to particles emitted from a radioactive substance, which are normally harmful to life forms. In an astronomical context, radiation is simply light of any kind emitted by an object, and it is not necessarily harmful in any way.

Explain why we have to observe stars and other astronomical objects from above Earth's atmosphere in order to fully learn about their properties.

It is important to observe the Sun and other astronomical objects in wavelengths other than the visible band of the spectrum. Due to Earth's atmosphere absorbs much of the ultraviolet light coming from space

If spectral line wavelengths are changing for objects based on the radial velocities of those objects, how can we deduce which type of atom is responsible for a particular absorption or emission line?

It is the precise wavelength (or color) that tells astronomers which lines belong to which element.

Explain what Joseph Fraunhofer discovered about stellar spectra.

Joseph Fraunhofer, discovered that there are more than 600 dark lines, which led scientists to rule out the boundary hypothesis

Explain why light is referred to as electromagnetic radiation.

Light is an example of electromagnetic radiation, which encompasses a broad spectrum of waves. Light is a traveling wave of oscillating electric and magnetic fields.

Describe how Bohr's model used the work of Maxwell.

Maxwell's theory of electromagnetism says that when a charged particle changes speed or direction, it should radiate an electromagnetic wave and lose energy. As electrons orbit the nucleus, they change their direction regularly and therefore should radiate energy and soon fall into the nucleus. Bohr proposed that in certain permitted orbits around the nucleus, the electrons can orbit without giving off waves and losing energy, which was a radical notion and part of the revolution of quantum mechanics.

Describe the techniques radio astronomers use to obtain a resolution comparable to what astronomers working with visible light can achieve.

Radio astronomers use interferometry, in which the measurements of several telescopes are combined in order to produce a result that is comparable to that generated by a single telescope as large as the distance between the separate telescopes. In this way, the resolution of the observation is greatly increased, approaching the resolution of visible-light and infrared telescopes.

Radio and radar observations are often made with the same antenna, but otherwise they are very different techniques. Compare and contrast radio and radar astronomy in terms of the equipment needed, the methods used, and the kind of results obtained.

Radio astronomy passively detects incoming radio energy from an astronomical source. It requires three basic components: a telescope, a spectrometer, and a detector. It can detect sources all the way to the edge of the visible universe. Radar, on the other hand, is an active technique. Radio waves are emitted from the instrument on Earth, bounce off a source, and are detected upon their return. Therefore, a radio emitter is required in addition to a detector. It can only be used to detect very close astronomical bodies, such as planets or asteroids.

Explain recombination

Recombination is the reverse, of ionization, one or more photons is emitted.

What is the significance of Rutherford's gold foil experiment?

Rutherford's Experiment Defines Nature of Atom: Dense Central Nucleus, Electrons Orbit at large distance

Explain how the Doppler effect works for sound waves and give some familiar examples.

Sound waves emitted by an object moving toward you are compressed and observed to have a higher pitch, or frequency. For objects moving away, the sound has a lower pitch. We hear this in cars or trains passing by us—first moving toward us and then away from us.

What are the differences between light waves and sound waves?

Sound waves move much more slowly than light and require some sort of medium to propagate (like air, water, or any solid). Light moves much more quickly (at the fastest speed possible in the universe) and does not require a medium. It can propagate through empty space.

Give examples of longitudonal waves:

Sound, slinky

How do you measure to speed of a wave?

Speed = frequency X wavelength (Speed, frequency, and wavelength of a wave = all related)

In black body radiation when an object is heated, it glows and we can measure its spectrum; ideally, a heated object radiates with a wavelength where the intensity is a maximum. How is the characteristic color of an object defined?

The characteristic color is defined by the wavelength of the maximum intensity, this is directly related to its temperature.

What is the photo-electric effect?

The effect is based on the idea that electromagnetic radiation is made of a series of particles called photons. When a photon hits an electron on a metal surface, the electron can be emitted. The emitted electrons are called photoelectrons.

Explain how we can deduce the temperature of a star by determining its color.

The higher the temperature, the shorter the wavelength at which the peak amount of energy is radiated. This is because in any solid or denser gas, some molecules or atoms vibrate or move between collisions slower than average and some move faster than average. So when we look at the electromagnetic waves emitted, we find a broad range, or spectrum, of energies and wavelengths. More energy is emitted at the average vibration or motion rate (the highest part of each curve), but if we have a large number of atoms or molecules, some energy will be detected at each wavelength.

Explain what the ionosphere is and how it interacts with some radio waves.

The ionosphere is a layer of charged particles at the top of our atmosphere, mostly ionized by interactions with sunlight and the solar wind. Some longer wavelength radio waves (such as AM radio) cannot penetrate this region and so the ionosphere scatters these waves in many directions. Under the right conditions, the ionosphere sometimes acts like a radio mirror, reflecting these waves back to the surface (hence the reason you can hear some powerful AM radio stations from more than 1,000 miles away at night).

What distinguishes one type of electromagnetic radiation from another? What are the main categories (or bands) of the electromagnetic spectrum?

The only characteristic that distinguishes one from another is its wavelength, or frequency. Gamma Rays, x rays, ultra-violet, visible, infrared, microwave, radio

Explain what dispersion is and how astronomers use this phenomenon to study a star's light.

The separation of different wavelengths of white light through refraction of different amounts

Explain the results of Rutherford's gold foil experiment and how they changed our model of the atom.

When Rutherford allowed α particles from a radioactive source to strike a target of gold foil, he found that, although most of them went straight through, some rebounded back in the direction from which they came. (From this experiment, he concluded that the atom must be constructed like a miniature solar system, with the positive charge concentrated in the nucleus and the negative charge orbiting in the large volume around the nucleus.

What does Heisenburg's uncertainty principle say?

This says I can know either the position of something very precisely, or the momentum (velocity), but not both at the same time! -This means that the future is not exactly calculable—no matter how big our computers are, there is uncertainty.

What kind of motion for a star does not produce a Doppler effect? Explain.

Transverse (sideways) motion (perpendicular to your line of sight to the object) does not produce a Doppler shift since there is no motion either toward or away from the observer.

What is wave-particle duality and what does it mean?

Wave-Particle Duality •It means that light and matter each behave in some experiments like waves, and in some experiments like particles.

Explain why glass prisms disperse light.

When white light passes through a prism, it is dispersed and forms a continuous spectrum of all the colors.

Can waves carry energy?

Yes! Waves carry energy, witness ships washed ashore from high waves during storms

Is it possible for two different atoms of carbon to have different numbers of neutrons in their nuclei? Explain.

Yes, Atoms with the same number of proton but different numbers of neutrons are defined as Isotopes and there elements remain the same. Think of isotopes as siblings in the same element "family"—closely related but with different characteristics and behaviors.

When you put a bunch of things together that are wiggling a different speeds what do you build?

a spectrum

Does light carry energy

duh

Is your textbook the kind of idealized object (described in section on radiation laws) that absorbs all the radiation falling on it? Explain. How about the black sweater worn by one of your classmates?

absorbs it, because it is not giving off any radiation on its own same goes for the black sweater

Where in an atom would you expect to find electrons? Protons? Neutrons?

protons are found in the nucleus (positive charge) neutrons found in the nucleus of helium atoms (not hydrogen). Contains same mass as a proton but carry no charge electrons found outside of the nucleus (negative charge) that orbit the nucleus

What an Atom is and Isn't

•A miniature "solar system" with the heavy nucleus playing the role of the Sun, and the electrons playing the role of the planets. The electrostatic (Coulomb) force between the positively charged ion and the negatively charged electrons plays the role of gravity. •But there is one HUGE difference: only certain orbits are allowed for the electron, ... but why?

What speed to electromagnetic waves travel at?

•All electromagnetic waves travel at the speed of light. • The speed of light in a vacuum is a constant, c .

How are continuum spectra produced?

•Continuum Spectra are produced by fully ionized, hot, dense (why?) material emitting photons, this is thermal radiation, or black body radiation. - collisions of free electrons and photon processes operate during ionization and recombination. Together these make the continuum spectra. -Thermal motions, or energy (set by T), of electrons "wiggles" charges, causing them to radiate photons (energy) with typical wavelength set by their T. This explains Wien's law. Works in reverse to explain near perfect absorption (BB) nature of thermal emitter.

What Properties of Light Can We Understand in the Wave Picture?

•Energy •Inverse square law •Color •Refraction •Interference •Diffraction •Diffraction •Dispersion

What is ionization and how does it happen?

•Ionization happens when and electron escapes: gains so much energy it escapes the attractive force of the nucleus. This happens in two ways: -1) Absorption of photons with energies greater than the highest bound state (a bit like the photo-electric effect) -2) Collisions with other electrons or atoms "bump" the electron up (see demo in Redshift)

What are the observed properties of the interactions between light and matter?

•There are only 4 ways light and matter interact 1)Transmitted 2)Absorbed 3)Reflected/Scattered 4)Emitted

What wavelengths does visible light encompass?

•Visible light ranges from 400 to 700nm.

How can you tell which element's spectra is being observed?

•Wavelengths of lines are unique for gases composed of different elements (see RedShift demo) -Spectra are marked with the unique fingerprint of each element