A-Level Physics OCR A Definitions
negative temperature coefficient (NTC)
A relationship in which variable decreases as temp increases NTC Thermistors
Mass
Amount of matter, a base quantity kg
angle of incidence
Angle between direction of travel of incident ray and normal
ampère
Base SI unit of electric current, A, current flowing in two parallel wires in a vacuum 1m apart such that atractive force 2.0*10-7 per metre length of wire between them
Ammeter
Device used to measure electric current-placed in series (ideally 0 resistance)
led
Diode that emits light when it conducts electricity
air resistance
Drag/resistive force experienced by objects moving through air
conservation of charge
Law where electric charge can neither be created nor destroyed-total charge must be same before and after interaction
radio waves
Long wavelength electromagnetic waves >10-1m
amplitude
Max displacement from equlibrium point of a particle in a wave
number density
Number of free electrons per cubic metre of material, symbol n, unit m-3
projectile
Object that is thrown or propelled on surface of earth
Primary Waves(P-Waves)
Primary waves- longitudinal waves that travel through Earth earthquakes
kelvin
SI Base unit of temperature
antiparallel
Same line but opposite directions
S-Waves
Secondary transverse waves that travel through Earth from an earthquake
X-rays
Short wavelength electromagnetic wave 10-8m to 10-13m used medical imaging
Principle of conservation of energy
Total energy of closed system remains constant-cannot be created/destroyed
potential divider equation
Vout=(R2/(R1+R2))xVin
turn-ratio equation
Vs/Vp = ns/np = Ip/Is
principle of superposition of waves
When 2 waves of same type meet at a point in space, their resultant displacement is the sum of their individual displacements
Kirchhoff's first law
at any point in electrical circuit, sum of currents into that point is equal to sum of currents out of that point. Electrical charge is conserved
ion
atom has either lost of grained electrons so has net charge
proton number
atomic number = no protons in nucleus
half-life
average time takes for half no active nuclei in a sample of an isotope to decay
mean drift velocity
average velocity of electrons as they move through a wire, symbol v, unit ms-1
loading(electrical)
connecting component across terminals of source of e.m.f or across another component
molar gas constant
constant in equation of state of ideal gas 8.31JK-1mol-1
Stefan constant
constant in stefans law L=4pir^2iotaT^4 luminosity of star to its surface area and absolute surface temperature
terminal velocity
constant speed reached by an object when drag force is equal and opposite to the weight of the object
exponential decay
constant-ratio process in which quantity decreases by same factor in equal time intervals
excited
containing an electron of electrons that have absorbed energy and boosted into higher energy level
brownian motion
continous random motion of small particles suspended in a fluid visible under microscope
standard model
current theory of particle physics quarks and electrons
heavy damping
damping that occurs when damping forces are large and period of oscillations increases slightly with rapid decrease in amplitude
light damping
damping that occurs when damping forces are small and period of oscillations is unchanged
attenuation
decrease in intensity of em radiation as passes through matter of space
white dwarf
dense star formed from core of red giant
volt
derived SI unit of P.D. and e.m.f. V. Energy transferred per unit charge. 1V is p.d. across componenet when 1J of energy transferred per 1C passing through component
coulomb
derived SI unit of electric charge, 1 coulombs passes a point in one second. 1C=1As
ohm
derived SI unit, Ω, resistance of component that has P.D of 1V per unit Ampere
kilowatt-hour
derived unit energy-1kWh=3.6MJ. Energy in kWh can be calculated by multiplying power by time
electronvolt
derived unit of energy-subatomic particles and photons. Energy transferred to/from electron when passes through P.D of 1V. 1eV = 1.6*10-19
I-V characteristic
description of relationship between electric current in component and p.d. accross it. I again V graph
cloud chamber
detector of ionising radiation vapour at low temp where liquid condenses around ionised particles
electricity meter
device that measures electrical energy supplied in kWh to a house from the grid
cell
device that transfers chemical energy into electrical energy
electron gun
device that uses accelerating potential difference to produce beam of electrons
ultrasound transducer
device used to generate and recieve ultrasound converts elec to sound and sound to elec
voltmeter
device used to measure p.d. must be in parallel and would have ideally infinite resistance
gold leaf electroscope
device with metallic stem and gold leaf used to measure electric charge used to be used as voltmeter for high voltages
phase difference
difference between displacements of particles along a waves. Degrees or radians.
mass defect
difference between mass of nucleus and mass of completely separated constituent nucleons
phase difference
difference in displacement between 2 oscillating objects identical adjacent points or displacement of oscillating object at different times
path difference
difference in distance travelled by 2 waves from source to specific point
right hand grip rule
direction field from direction which fingers right hand curl around wire
Lenz's law
direction of induced emf or current is always such as to oppose the change producing it
energy level
discrete amount of energy that electron within atom is permitted to possess
displacement (waves)
distance from equilibrium position in particular direction
light-year
distance travelled by light in a vacuum in a time of 1 year 9.46x10^15m
braking distance
distance travelled by vehicle from time brakes applied to full stop
thinking distance
distance travelled by vehicle from when driver sees reason to stop to when brakes applied
wave speed
distance travelled by wave per unit time
displacement
distance travelled in particular direction-vector with magnitude and direction
parsec
distance which radius of one AU subtends an angle of one arcsecond
Maxwell-Boltzmann distribution
distribution of speed of particles in a gas
resistance
dividing potential differnce across it by current in it Ohms
potential divider
electrical circuit designed to divide p.d. across 2 or more components to produce specific output
filament lamp
electrical component containing filament of wire converting electrical to light
resistor
electrical component that obeys ohms law
thermistor
electrical component which resistance that decreases as temperature increases(Negative temperature Coefficient)
potentiometer
electrical component with 3 terminals which can change p.d. between 2 terminals
ultraviolet
electromagnetic wave with wave length 4x10-7 to 10-8
microwaves
electromagnetic wave with wavelengths 10-1m to 10-3m
infrared waves
electromagnetic waves with wavelengths 10-3m to 10-7m
visible light
electromagnetic waves with wavelengths 4x10-7m to 7x10-7m
free electron
electron in metal not bound to atom-delocalised
photoelectrons
electrons emitted from surface of metal by photoelectric effect
neutron
elementary neutral particle hadron found in nucleus of atoms
quark
elementary particle exist in 6 forms and joins quarks to make hadrons
thermionic emission
emission of electrons from surface of hot metal wire
photoelectric effect
emission of photoelectrons from metal surface when electromagnetic radiation acts on metal
kinetic energy
energy associated with object as result of its motion
ground state
energy level with most negative possible value for electron within atom
specific heat capacity
energy required per unit mass to change the temperature by 1K measured jkg-1K-1
specific latent heat
energy required to change phase per unit mass while at constant temp
specific latent heat of vaporisation
energy required to change unit mass of substance from liquid to gas while at const. temp
specific latent heat of fusion
energy required to change unit mass of substance from solid to liquid while at const. temp
elastic potential energy
energy stored in a object due to its deformation
tensile force
equal and opposite forces acting on a material to stretch it
de Broglie equation
equation relating wavelength and momentum of a particle
grating equation
equation used to determine wavelength of monochromatic light sent through diffraction grating
x-ray tube
equipment that produces x ray photons by firing electrons from cathoded ray across large pd in evacuated tube, a ray photons produced when electrons decellerated hitting target metal of anode
velocity selector
everything that exdevice uses elec and magnetic fields to select charged particles of velocity by deflection
red giant
expanding star at end of its life with inter core where fusion no longer takes place but fusion of lighter elements continues in outer shell
tensile strain
extension per unit length (ratio no units)
Optical Fibre
fibre made of glass designed with verying refractive index to internally reflect pulses of light through it
gravitational field
field created around any object with mass extending to infinity but dinishing as mass further from centre of mass
node
for a stationary wave, a point where amplitude is always 0
principle of moments
for body in rotational equilibrium, sum anticlockwise equals sum of clockwise on same point
triple point
for substance, specific temp and pressure where all 3 phases of substance exist in thermodynamic equilibrium
force-extension graph
force against extension with area under graph=work done on material
Hooke's law
force applied is directly proportional to extention of spring unless limit of proportionality is exceeded
Newton's law of gravitation
force between 2 point masses is directly proportional to product of masses and inversely to square of separation between them F = Gm1m2/r2
normal contact force
force exerted by a surface on an object which acts perpendicular to the surface
pressure
force exerted per unit cross sectional area. Pascals
gravitational field strength
force exerted per unit mas at point within gravitational field
electric field strength
force experience per unit positive charge at that point
tensile stress
force per unit cross-sectional area Pa
restoring force
force that tries to return system to equilibrium position
centripetal force
force which keeps body moving with constant speed in circular path
natural frequency
frequency of free oscillation
driving frequency
frequency where periodic driver force applied to system in forced oscillation
electromagnetic spectrum
full range of frequencies of electromagnetic waves
elementary particle
fundamental article
lepton
fundamental particle or antiparticle that is not affected by strong nuclear force
aphelion
furthest point from sun in orbit
coupling gel
gel with acoustic impedance similar to skin gel used in ultrasound
Hubble constant
gradient of line of best fit for recessional speed against distance from earth
force-time graph
graph of net force against time, area under graph = to impulse
wave profile
graph showing displacement of particles in wave against distance along wave
Hertzsprung-Russell diagram
graph showing relationship between luminosity of stars and average surface temp
uniform gravitational field
gravitational field in whcih field lines are parallel and value for g remains constant
weight
gravitational force on an object N newtons
Planck constant
h, .63x10-34Js
baryon
hadron made with combination of 3 quarks
infalction
hase of acceleration of expansion of universe
protostar
hot dense sphere of condensing dust and gas on way to becoming star
red supergiant
huge star in last stages of life before explodes in supernova
oscilloscope
instrument that displays electrical signal as voltage against time
ionic solution
ionic compound dissolved in liquid to form electrolyte
beta radiation
ionising radiation consisting of fast moving electrons
gamma radiation
ionising radiation consisting of high energ photons wavelength 10^-13m at c
alpha radiation
ionising radiation of 2 proton 2 neutron particles
comet
irregular body of ice, dust and rock in highly eccentric orbit around sun
plastic deformation
irreversible change in shape of object due to compressive/tensile force
closed system
isolated system that has no interaction with surroundings
brittle
lack of ability of plasticity
gas laws
laws governing behaviour of ideal gases like Boyles law
red shift
lengthening of observed wavelength occurs when wave source moving away red-shifted
neutrino
lepton that carries no charge with minute mass less that millionth of electron
monochromatic light
light of a single frequency
spectral line
line in an emmision line soectrum or absorption line spectrum at specific wavelength
wavefront
line of points in phase with each other in a wave perpendicular to direction of energy transfer
isotherm
line on pressure volume graph connecting points of same temperature
Kepler's second law of planetary motion
line segment connecting planet to the sun sweeps out equal areas during equal intervals of time
gravitational field lines
lines of force used to show grav. pattern of object
electrolyte
liquid containing ions that are free to move so conduct electricity
hysteresis loop
loop shaped plot obtained when loading or unloading material produces different deformations
fundamental frequency
lowest frequency at which object can vibrate
absolute zero
lowest possible temp when substance has min internal energy
faradays law
magnitude of induced emf directly proportional to rate of cange of magnetic flux linkage
main sequence
main period of stars life during which it is stable
fiducial marker
marker for a point used as fixed basis for measurement of comparison
rest mass
mass of object such as particle when stationary
molar mass
mass of one mole of substance
Chandrasekhar limit
mass of stars core which electron degeneracy pressure sufficient to prevent gravitational collapse 1.44 solar masses
density
mass per unit volume of a substance
polymeric
material of long chain molecules-rubber
semiconductor
material with a low number density than a typical conductor
strong material
material with large value for ultimate tensile strength
trough
max negative amplitude of a transverse wave
ultimate tensile strength
max stress that material can withstand before breaks
peak
maximum positive amplitude of a transverse wave
astronomical unit
mean distance from earth to sun 150 million km
mean square speed
mean of squaraed velocities of particles in a gas
attenuation coefficient
measure of absorption of x ray photons by substance
amount of substance
measure of amount of matter in moles
eccentricity
measure of elongation of ellipse
relative charge
measurement of electric charge of particle in multiples of elementary charge
target metal
metal with high melting point used for anode in X-ray tube
carbon dating
method for determining age of organic material activites of carbon 12 and 14 nuclei of material
crystallography
method for determining structure of substance by studying interference patterns produced by waves passing through a crystal of substance
microwave background radiation
microwave signal of uniform intensity detected from environment fits profile for black body at temp 2.7K
escaoe velocity
min velocity which object has just enough energy to leave specified grav. field
wavelength
minimum distance between 2 identical adjacent points on a wave
work function
minimum energy needed to remove single elctron from surface of particular metal J
binding energy
minimum energy required to seperate nucleus into consistent protons and neutrons
threshold frequency
minimum frequency of the electromagnetic radiation that will cause the emission of electron from surface of a metal Hz
threshold voltage
minimum potential difference at which diode begins to conduct
arcminute
minute of arc 1degree=60 arcminutes
ideal gas
model of gas including assumptions that simplify behaviour
kinetic model
model that describes all substances made of atoms, ions or molecules arranged differently depending upon phase
conventional current
model used to describe electric current in a circuit-conventional current travels from positive to negative-but doesnt actually
Boltzmann constant
molar gas constant divided my avogadro constant-mean kinetic energy of atoms in gas to temperature
constant speed
motion in which distance per unit time is same
free oscillation
motion of mechanical system displaced from equilibrium position then allowed to oscillate without any external forces
free fall
motion of object accelerating under gravity with no other force acting
constant velocity
motion where change in displacement per time stays same
rarefaction
moving region which medium is less dense or has less pressure than surrounding medium
refractive index
n=c/v where c is speed of light and v is speed of light through material
cathode
negatively charge electrode
anion
negatively charged ion -attracted to anode
electron degeneracy pressure
pressure created by electrons in core of collapsing star due to Pauli exclusion principle
radiation pressure
pressure from photons in core of star acts outwards to counteract pressure from gravity pulling inwards
boyle's law
pressure of ideal gas inversey proportional to volume provided mass and temp do not vary
gas pressure
pressure of nuclei in stars core pushing outwards counteracting grav. force pulling matter into star
decay constant
prob of decay of individual nucleus per unit time
fusion
process in 2 smaller nuclei join
fission
process where large nucleus splits into 2 smaller after absorbing neutron
radioactivity
process which unstable nuclei split, decay emitting ionizing radiataion alpha beta or gamma
time constant
product of capacitance and resistance for capacitor resistor circuit-time taken for PD to decrease to e^-1 of initial value when capacitor discharges through resistor
magnetic flux
product of component of magnetic flux density perpendicular to a given area and that cross-sectional area: ∅=BAcosθ
acoustic impedance
product of density of substance and speed of ultrasound
work
product of force and distance moved in direction of force J
moment
product of force and perpendicular distance from a pivot or stated point
magnetic flux linkage
product of number of turns in coil and magnetic flux density Weber turns
torque
product of one of forces in couple and perpendicular distance between forces
piezoelectric effect
production of emf by crystals when compressed, stretched twisted or distorted
ductile
property of a material that has large plastic region in a stress-strain graph
resistivity
property of material measures in Ohms
linear momentum
property of object travelling in straight line. Mass * velocity
tension
pulling force exerted by a string, cable or chain on an object
force
push or pull on object N
force constant
quantity for dividing force by extension for object obeying hookes law
derived quantity
quantity that comes from base units
vector quantity
quantity with magnitude and direction
photon
quantum of electromagnetic energy-photon energy E is E=hf where h is planck constant f is frequency of electromagnetic radiation
intensity(waves)
radiant power passing through surface per unit area
corrected count rate
radiation count rate measured in experiment minus background
background radiation
radiation emitted by surrounds
radiopharmaceutical
radioisotope chemically combined with elements that will target tissues to ensure radioisotope reaches correct organ or tumor
angular velocity
rate of cange of angle for moving object in circular path
average velocity
rate of change of displacement in time
Newtons Second Law of motion
rate of change of momentum of an object is directly proportional to the resultant force in direction of force
activity
rate of nuclei decay in radioactive source becquerels
Young modulus
ratio of tensile stress to tensile strain when these quantities are directly proportional to each other Pa
intensity reflection coefficient
ration of reflected intensity over incident intensity for ultrasound incident at boundary
efficiency
ration of useful output energy to total input energy (%)
chain reaction
reaction where neutrons released trigger exponential growth in rate of reactions
hubbles law
recessional speed v of galaxy is directly proportional to its distance from earth
nucleus
small positive charged region in centre of atom where most mass concentrated
elementary charge
smallest sum of electric charge. 1.6*10-19
quantisation
some quantities sucha s energy or charge are made of lumps of base quantities
wave source
source waves object moving to relative view causes doppler effect
continuous spectrum
spectrum where all visible frequencies or wavelengths are resent
instantaneous speed
speed at moment it is measured-speed over infinitely small time interval
Kepler's third law of planetary motion
square of orbital period T of planet is directly proportional to cube of its average distance from the sun
root mean square speed
square root of mean square speed
thermal equilibrium
state where no net flow of thermal energy
magnetic flux density
strength of magnetic field F/IL where F force acting on current carrying conductor placed at right angles to magnetic field, I is current in conductor L is Length of conductor in magnetic field Symbol B unit Tesla T
breaking strength
stress value at point of fracture-breaking force diveded by cross sectional area
plumb-line
string with weight used to provide vertical reference line
fluid
substance that can flow-liquids and gases
coolant
substance that removes thermal energy from reactors
moderator
substance used to slow down fast neutrons produced in fission reactions so they propagate fission reaction
internal energy
sum of randomly distributed kinetic and potential energies of atoms, ions or molecules within substance
interference
superposition of 2 progressive waves from coherent sources to product a resultant wave with displacement equal to sum of indiv. displ. of waves
destructive interference
superposition of 2 waves in antiphase so the waves cancel each other out and resultant wave has smaller amplitude than original waves
constructive interference
superposition of 2 waves in phase so resultant wave has greater amplitude than original waves
radial field
symmetrical field that diminished with distance^2 from centre
spectroscopy
technique in physics that uses spectral lines to identify elements present in others
stellar parallax
technique used to determine distance of starts by conparing apprent distances again itself 6 months apart-wobble
celsius scale
temp scale 100 degrees between freezing point and boiling of water
acceleration
Rate of change of velocity. Vector quantity
power
Rate of work done Watts
planetary nebula
outer layers of red giant drifted into space leaving core behind at centre as white dwarf
superposition
overlap of 2 waves at a point in space
equation state of ideal gas
pV=nRT where n is no moles of gas
couple
pair of equal but opposite forces acting on a body but not in straight line
scintillator
part of gamma camera from sodium iodide which produces thousands of photons of visible light when struck by single gamma photon
collimator
part of gamma camera, thin tubes of lead absorbing photons arriving at angle to axis of tubes so picture obtained
nucleon
particle in nucleus of atom either proton or neutron
hadron
particle of antiparticle affected by strong nuclear force
fundamental particle
particle that has no internal structure and cannot be split into smaller particles
charge carrier
particle with charge that moves through material to form electric current
in phase
particles oscillating perfectly in time and position with each other
out of phase
particles that are neither in phase or antiphase are out of phase
interference pattern
pattern of constructive and desctructive interference formed as waves overlap
wlen's displacement law
peak wavelength at which intensity of radiation from black body is maximum is inversly proportional to absolute temp of black body
phase
phase of matter in state
diffreaction
phenomenon of waves passing through a gap or around an obstacle spread out
solar system
planetary system of star and at least one planet in orbit
diffraction grating
plastic slide with spacings that diffract visible wavelengths of light
pivot
point about which body can rotate
maximum waves
point of greatest amplitude on interference pattern from constructive interference
minimum(waves)
point of least amplitude in interference pattern, produced by destructive interference
yield point
point on stress strain graph beyond where deformation is no longer entirely elastic
centre of mass
point through which any fexternal force applied makes straight line motion but no rotation
cation
posiively charge ion that is attracted to cathode
proton
positively charged particle, hadron found in nucleus of atoms
terminal p.d.
potential difference across a electrical power source-when there is no current, this is equal to e.m.f of power source but if current the source is equal to e.m.f - lost volts
Archimedes' Principle
Upthrust on a object in fluid equals weight of fluid it displaces
Ohms Law
V is directly proportional to I provided KEPT AT CONSTANT TEMPERATURE
upthrust
upward bouyant force exerted on a body immersed in fluid
impedance matching
use of 2 substances with similar acoustic impedance to minimise reflection
wave equation
v=fλ where v = speed, wavelength = λ and f = frequency
elastic limit
value of stress or force beyond which elastic deformation becomes plastic deformation-object will not return to original shape or size after force released
limit of proportionality
value of stress or force beyond which stress is no longer directly proportional to strain
velocity
vector quantity equal to rate of change of displacement
Doppler equation
velocity of observed over light
fundamental mode of vibration
vibration at fundamental frequency
magnetic field pattern
visual representation of direction and strength of magnetic field
longitudinal wave
wave in which medium is displaced in same line as direction of energy transfer-oscillation of medium particles are parallel to direction of energy transfer
transverse wave
wave in which medium is displaced perpendicular to direction of travel of wave
stationary wave
wave that remains in constant position with no net transfer of energy and is characterized by its nodes and antinode
standing wave
wave that remains in constant position with no net transfer of energy and is characterized by its nodes and antinodes
progressive wave
wave which peaks and troughs/compressions and rarefractions move through medium as energy is transfered
equilibrium
when body in equilibrium, net force and moment acting are 0
superconductivity
where resistivity of material falls to almost 0 when material is cooled below certain temperature
harmonic
whole number multiple of fundamental frequency
electric potential
work done by external force per unit positive charge to bring charge from infinity in field
electromotive force (e.m.f)
work done on charge carriers per unit charge (V) measured accross a cell, battery or power supply
gravitational potential
work done per unit mass to bring object to point in grav field
photomultiplier tube
apparatus that converts photon of visible light to electrical pulse
electric charge
(Q)physical property + or - measured in coulombs C
impulse
area under force time graph-product of force and time for which force acts
series
arrangement of electrical components connected end to end meaning current is same in each component
compressive force
2 or more forces acting together that reduce length of volume of object
resistor circuit
2 or more resistors arranged to provide specific reisstance
acoustic matching
2 substances with similar acoustic impedance to minimise reflection of ultrasound at boundary
triangle of forces
3 forces acting at a point in equilibrium
Abogadro constant
6.02*10^23 no atoms in 12g of carbon 12
Newtons First Law of motion
A body will remain at rest or continue to move at constant velocity unless acted upon by a resultant force
scalar quantity
A quantity with magnitude but no direction
Newtons Third Law of motion
Body A acting on body B exerts an equal but opposite for to Body B acting on Body A
cosmological principle
assumption that universe is homogeneous and isotrophic
normal
Imaginary line perpendicular to a surface such as boundary between one medium and other
Kirchhoff's second law
In a closed loop of an electrical circuit, sum of e.m.f.s is equal to sum of p.d.s
magnetic field lines
Lines of force drawn to represent a magnetic field pattern
average speed
Rate of change of distance in time
lost volts
P.D accross inernal resistor of source of e.m.f
antiphase
Particles ocillating where one reaches max displ. whilst other reaches min displ.
Maximum (waves)
Point of greatest amplitude in a interference pattern, produced by constructive interference
Acceleration of free fall
Rate of change of velocity of object falling in a gravitational field
medical tracer
compound labelled with radioisotope traced inside body using gamma camera
SI
Systeme International d'Unites
potential difference
Work Done per unit charge through component
non-ohmic component
a component that doesn't obey ohms law e.g. filament lamp or diode
compression
a region in which medium is denser or has higher pressure than surrounding medium
stiffness
ability of an object to resist deformation
absorption coefficient
absorption of x ray photons by substance atenuation coefficient
centripetal acceleration
acceleration of any object travelling in circular path at constant speed. Always acts towards centre of circle
mass
amount of matter measure in kg
mole
amount of substance that contains elementary entities as atoms 0.012kg of carbon 12
angle of reflection
angle between direction of travel of reflected ray and normal
law of reflection
angle of incidence = angle of reflection
critical angle
angle of incidence at boundary between 2 media will product an angle of refraction of 90 degrees
Parallax angle
angle of shift in position of relatively close star again backdrop of more distnace starts due to orbit-wobble
antiparticle
antimatter counterpart of particle with opposite charge to particle and same mass
positron
antiparticle of electron
ionising radiation
any form of radiation that can ionise atoms by removing an electron to leave a positive ion
meson
any hadron comprising of combo of quark and anti-quark
Coulombs law
any two point charges exert electrostatic force on each other directly proportional to product of charges and inversely to square of their seperation
binding energy per nucleon
binding energy divided by no protons/neutrons in nucleus-greater binding, more tightly bound to nucleus
planetary satellite
body in orbit around planet
satellite
body orbiting around planet
energy
capacity for doing work Joules
GPE
capacity for object doing work as result of objects position in gravitational field
refraction
change in direction of wave as it changes speed when passes from one medium to another
reflection
change in direction of wave at boundary between 2 different media so wave remains in same medium
Doppler effect
change in frequency and wavelength of waves received from object relative to observer
compressive deformation
change in shape of object due to compressive forces
tensile deformation
change in shape of object due to tensile forces
gradient
change in vertical axis quantity divided by corresponding change in horizontal axis quantity
capacitance
charge stored er unit potential difference across capacitor
perihelion
closest point to sun in orbit
nebula
cloud dust/gas hundreds size of galaxy
battery
collection of cells that transfer chemical energy to electrical energy
galaxy
collection of stars or dust bound together by mutual gravitational force
inelastic collision
collision in which kinetic energy is lost
perfectly elastic collision
collision where no kinetic energy is lost
capacitor
compenent that stores charge, consists of 2 plates seperated by an insulator
annihilation
complete destruction of article and antiparticle releasing energy in form of photons
dark energy
hypothetical form of energy that neither emits nor absorbs light
expanding universe
idea that space and time always expanding
centre of gravity
imaginary point at which entire weight of object appears to act
supernova
implosion of red supergiant at end of life which leads to ejection of stellar matter into space leaving invert core
resonance
increase in amplitude of forced oscillation when driving frequency matches natural frequency of oscillating system
extension
increase in length of object when tensile force exerted
thermal neutron
neutron in fission reactor with mean kinetic energy similar to therman energy of particles in reactor
frequency
no complete oscillations per unit time
induced fission
nuclear fission when nuclear becomes unstable on absorbing another particle
isotopes
nuclei of same element that have same atomic number but different nucleon numbers
daughter nucleus
nucleus formed following radioactive decay
atomic number
number of protons in nucleus
frequency(waves)
number of wavelengths passing a point per unit time
planet
object in orbit around star with mass large enough for gravity to give round shape. Undergoes no fusion reactions and has cleared its orbit of most other objects
black body
object that absorbs all electromagnetic radiation or when in thermal equilibrium emits distribution of wavelengths at specific temerature
black hole
object which has escape velocity greater than speed of light so not even photons can escape
weak nuclear force
one 4 fundamental forces in nature for inducing beta decay in unstable nuclei
atomic mass unit
one atomic mass unit is 1/12 mass of neutral carbon 12 atom
strong nuclear force
one of 4 fundamental fforces in nature acting on hadrons holding nuclei together
base unit
one of 7 units that form building blocks of SI measurements
negative (charge)
one type of electric charge, like repel, dislike attract
Kepler's first law of planetary motion
orbit of planet is ellipse with sun at one of the two foci
simple harmonic motion
oscillating motion where acceleration of object is directly proportional to its displacement but in opposite direction a=w^2x
damping
oscillation damped when external force acts on oscillato has effect of reducing amplitude of oscillations
forced oscillation
oscillation where periodic driver force applied to oscillator
polarisation
oscillations of transverse waves limited to one plane
isochronous oscillator
oscillator that has same period regardless of amplitute
angular frequency
oscillatory motion-frequency times 2pi
total internal reflection
reflection of all light hitting a boundary between 2 media back into original medium when light is travelling through medium with higher refractive index, incident angle is greater than critical angle
internal resistance
reistance of a source of e.m.f.-causes loss in energy/voltage as charge passes through source
neutron star
remnant core of massive star gone supernova collapsed under own gravity due to high density entirely neutrons
oscillating motion
repetitive motion of object around equilibrium position
pair production
replacement of single photon with particle and antiparticle of same total energy
free-body diagram
represents all forces acting on single object
LDR
resistance decreases as light intensity incident on it increases
drag force
resistive force exerted by a fluid on an object moving through it
equilibrium pos (waves)
resting position for particles in medium
elastic deformation
reversible change in shape of object due to compressive or tensile force-removal of stress or force will return the object to original shape and size
control rods
rods made of material whose nuclei absorb neutrons
conical pendulum
rotates in circle at constant speed
isotropic
same in all directions
geostationary satellite
satellite that remains in same pos relative to spot on earths surface-orbit 24 hours
absolute scale of temperature
scale for measuring temp based on absolute 0 and triple point of water Kelvin
arcsecond
second of arc 1arcminute=60 arcseconds
diode
semiconductor component that allows current only in one direction
grating spcing
seperation between adjacent lines or slits in diffraction grating
emission line spectrum
set of specific frequencies of em radiation visible as bright lines on spectroscope
absorption line spectrum
set specific frequencies of em radiation visible as dark lines on spectroscopy. Absorbed by atoms as electrons excited between energy states by absorbing corresponding amount energy inform of photons
gamma rays
short-wavelength electromagnetic waves *10-10m to *10-16m
blue shift
shortening of observed wavelength tat occurs when wave source moving towards observer
big band
theory that all matter was contained in sigularity
wave particle duality
theory that states that matter has both particle and wave properties and electromagnetic radiation has wave and particulate nature
polycrystalline graphite
thin layers of graphite with regularly arrange carbon atoms in different orientations
timebase
time interval represented by one horizontal square on oscilloscope screen
period(waves)
time taken for one complete wavelength to pass a given point
period
time taken to complete one full oscillation
stopping distance
total distance travelled from when driver sees reason to when vehicle stops. Sum of thinking distance and braking distance
principle of conservation of momentum
total moment of a system remains same before and after a collision or explosion
luminosity
total radiant power output of a star L Watts
step-down transformer
transformer with fewer turns on secondary than on primary
step-up transformer
transformer with more turns on secondary that primary and higher output voltage than input
partially polarised
transverse wave in which more oscillations in one plane that rest, but not fully plane polarised
plane polarised
transverse wave in which oscillations are limited to one plane
unpolarised
transverse wave where oscillations occur in many planes
vector triangle
triangle constructed to scale to determine resultant of 2 vectors
coherence
two waves that are coherent have same constant phase difference
parallel circuit
type of branching electrical circuit where more than one path for current. P.D. is constant I splits up
polarity
type of charge or orientation of cell relative to a component
positive
type of electric charge, pos attract neg. repel other pos
series circuit
type of electrical circuit where components are connected end to end
homogeneous
uniform in terms of distribution of matter across universe
becquerel
unit of activity-one decay per second