# Flashcard glossary

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absolute uncertainties | Plus or minus the uncertainty |

absolute zero | The lowest temperature possible zero K |

acceleration | The rate of change of velocity |

accurate measurement | close to the accepted value |

activity | The rate of decay |

adiabatic transformations | No exchange of heat |

air resistance | The force of air opposing motion |

air wedge interference | The interference of light reflected off to angled glass plates |

albedo | The ratio of scattered light to incident light |

Algodoo | application used to simulate motion |

alpha particles | Helium nuclei emitted by unstable nuclei. |

alpha scattering experiment | High-speed positive particles fired at a thin gold foil. |

alternating current (AC) | Electric current that changes direction and magnitude. |

alternators | A rotating magnet in a coil. |

ammeters | Device for measuring current. |

amp (unit) | The Unit of current same as Coulomb per Second |

Ampere | 1A causes a force of 2 x 10^-7 N between to long conductors 1 m apart in a vacuum |

amplitude | Height of a wave measured from equilibrium position |

amplitude | The maximum displacement of a pendulum. |

ancient Greeks | Philosophers a long time ago |

angle of incidence | The angle between the normal and the incident ray. |

angle of reflection | The angle between the normal and the reflected ray. |

angle of refraction | The angle between the Normal and the refracted ray. |

angular displacement | The angle swept out by the radius. |

angular frequency | The angle swept out per unit time. |

Angular momentum | mvr |

angular velocity | The angle swept out per unit time |

annihilation | particle + antiparticle = energy but no mass |

antimatter | Matter made up of anti particles |

antineutrinos | Antiparticle of neutrino |

antinodes | Positions on a standing wave with zero amplitude. |

antireflective coating | An application of thin film interference |

apparent brightness (stars) | Brightness from the Earth |

apparent magnitude (stars) | Brightness from 10 pc |

area under a-t graph | change in velocity |

area under force - time graph | Work |

area under force distance graph | Work |

area under graph | area under the line |

area under v-t graph | displacement |

asteroids | Rocks orbiting the sun |

astronomical units | Sun - Earth distance |

atmospheric pressure | The pressure exerted by air. |

atom bombs | Application of an accelerating chain reaction. |

atomic lattice | A regular arrangement of atoms |

atomic line spectra | The spectrum formed when a low pressure gas is excited. Evidence of discrete electron energy levels. |

atomic nuclei | Heavy, small, positive centre of an atom |

atoms | Smallest particle of an element. |

attenuation | Reduction in amplitude |

Aurora Borealis | Glow in the night sky in the north due to the interaction betweencharged particles and the atmosphere |

average value of sine function | 00-Jan |

average velocity | Displacement / time |

average velocity | displacement/time |

Avogadro's number | The number of particles in a mole. |

background radiation | Radiation in a room due to naturally occurring radioactive material |

balanced forces | Condition for no acceleration. |

baryons | A group of particles including proton and neutron. |

batteries | Cells in series. |

BE (see binding energy) | The work done to take a nucleus apart or energy released when it is formed. |

becquerel (unit) | Unit of activity. |

best fit line | A line drawn as close as possible to the data points |

beta particles | An electron formed when a neutron changes to a proton. |

Big Bang | A model for the start of the universe. |

big crunch | A model for the end of the universe. |

binary stars | Pairs of stars that orbit each other. |

binding energy (BE) | The work done to take a nucleus apart or energy released when it is formed. |

black holes | The fate of massive stars. |

blue shift | Doppler shift in approaching sources of light. |

Bohr model | Atomic model assuming angular momentum to be quantised |

boiling | Change of state from liquid to gas. |

boron control rods | Absorb neutrons slowing down the chain reaction |

Brownian motion | The randon motion of smoke particles knocked about by air molecules. |

buoyancy | Upward force due to displacement of fluid. |

capacitance | charge/potential |

capacitors | Charge storing devices, usually parallel plates. |

capacitors in parallel | C = C1 + C2 |

capacitors in series | 1/C = 1/C1 + 1/C2 |

Carnot cycles | A thermal cycle comprising of isothermal and adiabatic changes. |

cells | A single unit of a battery |

Celsius scale | Temperature scale based on the melting point (0) an boiling point (100) of water. |

Celsius scale | Temperature scale based on the freezing and boiling of water. |

centre of mass | Point at which forces can be taken to act. |

centripetal acceleration | Acceleration towards the centre of a circle |

centripetal force | Force that causes circular motion, directed towards the centre. |

Cepheid variable | A star with varying brightness. Time period is related to luminosity |

CERN | A facility near Geneva with a huge particle accelerator. |

chain reactions | A nuclear reaction where one fission initiates another. |

Chandrasekhar limit | Defines the maximum size of a white dwarf. |

circular motion frequency | Number of complete cycles per second. |

circular wavefronts | Wave fronts from a point source. |

closed universe | A universe that stops expanding and then begins to contract. |

cloud chamber | Particle detector showing paths as vapour trails |

coal-fired power stations | Coal is burnt to give heat used to drive a turbine |

coalitions | Two bodies join together, example of inelastic collision |

coherence | Light sources with the same frequency and constant phase relationship. |

coherent | similar amplitude,same frequency constant phase difference. |

colour | related to wavelength |

colour charge | The property of quarks responsible for the strong force. |

colour mixing | red + green = yellow, green + blue = cyan, red + blue = magenta |

comets | Balls of ice with long tails orbiting the Sun. |

components | Fcos(angle) and Fsin(angle) |

Compton scattering | Interaction between a photon and electron demonstrating particle nature of light. |

concave lenses | Caves go in |

conduction | Transfer of heat via molecular vibration. |

conductors (electricity) | Materials that allow the flow of charge, mainly metals as they have free electrons. |

conservation of charge | Charge can not be created or destroyed. |

conservation of energy | Energy can neither be created or destroyed. |

conservation of momentum | Provided no external forces act, the momentum of a system of bodies is always the same. |

constellations | Ancient civilizations playing join the dots with the stars. |

constructive interference | Addition of waves that are in phase. |

continuous spectra | Spectra produced when e.g. Solids are heated |

convection | Transfer of heat in fluids due to reduced density with rise in temperature |

convex lenses | A converging lens, not a cave. |

cornea | The front surface of the eye, also acts to focus light. |

cosmic background radiation | Microwaves that are the result of expanding space increasing the wavelength of high energy radiation that existed in the early stages of the universe. |

cosmic rays | High energy particles entering the Earths atmosphere |

coulomb (unit) | The unit of charge. |

Coulomb's law | The force between two charged points is proportional to the product of their charge and inversely proportional to their separation squared. |

critical angle (refraction) | Angle on incidence when angle of refraction = 90 degrees |

critical damping (oscillations) | System returns to equilibrium without passing through it. |

critical density (universe) | Density of universe that predicts that expansion stops at infinite size. |

CT scans | A 3D X-ray |

cubic | of the form y= Ax^3 +Bx^2 + Cx + D |

damping | The reduction in amplitude of an oscillator due to an opposing force. |

dark energy | The reason why the expansion of the universe is accelerating. |

dark matter | Large amounts of matter predicted to exist in the universe but not seen. |

Davidson‚Germer experiment | An electron scattering experiment. Evidence for the wave nature of electrons. |

DC | Direct Current |

de Broglie hypothesis | All matter has wave like nature. |

de Broglie wavelengths | h/p |

decay | The changing of a nucleus by the emission of radiation. |

decay chains | A series of radioactive decays. |

decay constants | High value means rapid decay |

decimal places in value | same as uncertainty. |

deep inelastic scattering | Evidence for the existence of quarks. |

degradation of energy | Energy becomes more spread out. |

density | Mass/volume |

depleted uranium | Non fissile Uranium |

derived units | Not fundamental. Like density = mass/volume |

destructive interference | Two waves coincide and cancel out |

diffraction | The spreading out of a wave as it passes through a narrow opening. |

diffraction envelope | The effect of diffraction on multiple slit interference |

diffraction grating | Many equaly spaced parallel slits. |

dipoles | pairs of + and - charges |

direct current (DC) | Always in the same direction |

discharge tubes | Tubes of low pressure gas excited by an electric field. |

dispersion | The splitting up of colours by a prism. |

displacement | Distance moved in a particular direction. A vector quantity. |

displacement‚time graphs | Graph of displacement vs time. |

distance | Path length. |

Doppler effect | Change of frequency due to relative motion of source and observer. |

double slit experiment | Passing light through two parallel slits to give interference fringes. |

drift velocity | Average velocity of electrons moving through a conductor. |

dynamos | A rotating coil in a magnetic field used to produce electricity. |

echo | Reflection of sound |

EEEow | Sound of car passing stationary observer. |

efficiency | Energy delivered/Energy generated |

Einstein rings | Rings of light caused by the curvature of space - time by massive bodies. |

Einstein's postulates | Speed of light in a vacuum is constant and all inertial observers are the same. |

Einstein‚ principle of equivalence | Accelerating frames of reference are equivalent to those in gravitational fields. |

elastic collisions | KE and momentum conserved |

elastic collisions | Momentum and KE conserved. |

elastic PE | kx^2/2 |

electric charge | The property responsible for the electric force. |

electric currents | Movement of charge. |

electric field strength | Force/charge |

electric forces | The force between charged bodies |

electric potential | The work done per unit charge in taking a small positive test charge from infinity to a point. |

electric potential energy | The work done per unit charge in moving a small positive test charge from A to B |

electric power | p = VI = I^2R = V^2/R |

electromagnetic induction | Generation of EMF in a conductor due to changing magnetic field. |

electromagnetic waves | The propagation of changes in electric and magnetic field |

electron | A negatively charged particle that can be removed from an atom. The charge carrier in metals. |

electron energy levels | The discrete energies of atomic electrons. |

electron guns | electrons liberated from a hot wire accelerated through a potential difference. |

electron-volt (unit) | The energy gained by an electron accelerated by a PD of 1 V |

elements | Atoms with different numbers of protons. |

EM waves | The propagation of changes in electric and magnetic field |

emf | The amount of chemical / mechanical energy converted to electrical per unit charge in a battery / generator. |

emissivity | Power emitted per unit area by a body / power emitted per unit area by a black body |

energy | The ability to do work / Transferred when body A does work on body B. |

energy density | Energy per unit volume |

engines | Convert heat into work. |

enrichment | The process of increasing the % of fissile material in nuclear fuel. |

equation of state | PV = nRT |

equilibrium position | The position in which a system come to rest. |

equipotential lines | Lines joining points of equal potential. |

equipotential surfaces | Surfaces joining points of equal potential. |

error bar | A line drawn on a point to represent uncertainties |

errors | Uncertainties in measurement. |

escape speed | Speed required for a projectile to reach an infinite distance from a massive body. |

escape speed from Earth | 11 km/s |

evaporation | Liquid changing to gas at the surface. |

events | Charges taking place at a given position and time. |

exchange forces | Forces that are the exchange of particles |

explosions | Two bodies pushed apart, example of inelastic collision |

exponential decay equation | y = mx + c |

exponential equations | y=e^x |

fairies | Small people with wings. |

Faraday's law | Induced EMF equals the rate of change of flux enclosed. |

Feynman diagrams | Used to represent particle interactions, lines do not represent particle paths. Time progresses left to right (sometimes drawn with time going up) |

Feynman rule 1 | straight lines are particles wavy lines are photons |

Feynman rule 2 | each vertex has 2 straight one wavy line |

Feynman rule 3 | time progresses left to right (sometimes drawn with time going up) |

Feynman rule 4 | particles point forwards in time antiparticles backwards. |

Feynman rule 5 | there is always one arrow entering and one leaving. |

field lines | Show strength (line density) and direction (arrow) of field. |

first law of thermal dynamics | work done = gain in internl energy + heat lost |

flat universe | there is always one arrow entering and one leaving. |

Fleming's left hand rule | Motors: First- field, seCond - current, thuMb - motion |

Fleming's right hand rule | Generators: First- field, seCond - current, thuMb - motion |

fluorescent | A material that emits light when hit by electrons. |

flux (magnetic fields) | Flux density x Area |

flux density | Measure of the strength of magnetic field B = F/IL |

force | Push and pull |

force on a charge | F = Bqv |

force on a wire | F = BIL |

forced oscillation | An oscillation pushed by an external force. |

frames of reference | A coordinate system an observer uses to take measurements. |

free body diagrams | Forces drawn that act on a body but not forces exerted by the body |

free electrons | Electrons free to move about in conductors. |

frequency | Number of complete cycles per second. |

frequency (wave) | The number of complete wavelengths passing a point per second. |

frictional force | Force that opposes the relative motion of two in contact surfaces. |

fringe spacing | distance between bright lines in an interference pattern. |

fuel density | energy/volume |

fuels | Materials that can be burnt giving out heat energy. |

fundamental units | kg, m, A, s |

g (acceleration due to gravity) | 9.8 m/s^2 |

G (universal gravitational constant) galaxies | F = GMm/r^2 |

Galilean transforms | Non relativistic transformations between frames of reference. |

gamma radiation | High energy EM radiation. |

gas pressure | due to change in momentum of gas molecules hitting a wall. |

gases | Made of a large number of randomly moving atoms with no interatomic force. |

gauge bosons | Exchange particles e.g. photon |

Geiger‚Marsden experiment | Classic alpha scattering by Gold foil. |

general relativity | Relativistic theory of gravity. |

generations | Classification of fundamental particles |

generator | Converts KE into electrical anergy |

GeoGebra | Mathematics application |

geostationary satellites | Communication satellites with 1 day time period. |

global warming | Rise in temperature due to enhanced greenhouse effect. |

gluons | Exchange particle responsible for the strong force between quarks. |

GM tube | Particle detector |

gradient of acceleration time graph (constant acceleration) | zero |

gradient of s-t graph | velocity at one moment in time. |

gradient of v-t graph | acceleration |

gradients | Change in y / Change in x |

gravitational fields | Region of space where a mass experiences force. |

gravitational mass | m = F/g |

gravitational potential | Work done per unit mass taking a small test mass from infinity to a point. |

gravitational potential energy | Work done taking a body from infinity to a point. |

gravitational red shift | Increase in wavelength of receding galaxies due to Doppler shift |

hadrons | A particle made of quarks. |

Hafele‚Keating experiment | A relativistic experiment sending clocks around the Earth. |

half-lives | Time taken for radioactive activity to reduce by half. |

harmonics (sound) | Multiples of the lowest frequency standing wave formed in strings and pipes. |

Harvard classification | Be A Fine Girl Kiss Me. Stellar classification |

heat | Transferred when a hot body is in thermal contact with a cold one. |

heat capacity (see specific heat capacity | Amount of heat required to raise the temperature of a body by 1 K. |

heat pumps | Take heat from a cold body to a hot one. |

Heisenberg's uncertainty principle | ΔxΔp = h/4π or ΔtΔE = h/4π |

hertz (unit) | Cycles per second |

Hertzsprung‚Russell (HR) diagrams | Stellar diagrams on which stars are plotted according to luminosity and temperature. |

Higgs boson | Fundamental particle responsible for mass. |

Hooke's law | Force is proportional to extension. |

horizontal component (angle A measured to horizontal) | FcosA |

horizontal motion (projectile) | constant velocity |

horse power (unit) | 0.75 kW |

Hubble constant | Constant relating recessional velocity of galaxies to distance from the Earth. |

Huygens construction | A wavefront behaves as if made of an infinite umber of wavelets. |

hydroelectric power | PE stored in bodies of water converted to electrical energy. |

hydrogen | Smallest element, proton number = 1 |

hydrogen bomb | Uses fussion to create an explosion. |

hysteresis | Magnetic memory |

I-V graphs | Current vs Voltage used to determine resistance. |

ice cores | Samples of ice used to measure changes in the atmosphere over time. |

ideal gases | Obeys the gas laws. |

images | Positions where rays of light cross over. |

impulse | Change of momentum. |

Induced EMF in straight wire with velocity v perpendicular to field | BLv |

induction braking | Uses induced current to oppose motion. |

induction hotplates | Uses changing magnetic field to excite magnetic dipoles raising temperature. |

inelastic collisions | Momentum but not energy conserved. |

inertial frames of reference | A system of coordinates in which Newton's laws of motion are obeyed. |

inertial mass | Ratio Force/acceleration |

infrared (IR) radiation | EM radiation between red and microwave. |

instantaneous velocity | Velocity at one moment in time. |

Instantaneous velocity | very short displacement/time |

insulators (electricity) | Materials with no free electrons. |

intensity | Power per unit area. Proportional to A^2 |

interatomic force | Force between atoms, replulsive when close attractive when distant. |

interference | The addition of displacement when two waves meet. |

internal energy | Sum of KE + PE of molecules of a body. |

internal resistance | Resistance of internal components of a battery. |

inverse square relationship | y = k/x^2 |

ionization | Removal of electrons from an atom. |

iris | adjusts aperture of the eye |

iris | Part of the eye that controls size of apperture. |

isobaric transformations | Expansions / contractions where there is no exchange of heat. |

isochoric transformations | Constant volume expansions / contractions |

isolated systems | A system of bodies where no external forces act. |

isothermal transformations isotherms | Constant temperature expansions / contractions |

isotopes | Nuclei with the same proton number different neutron number. |

joule (unit) | Unit of energy. |

katabatic winds | Cold air coming down a mountain. |

Kelvin scale | Temperature scale based on the pressure of a fixed volume of gas. |

Kepler's third law | Time period of planets squared is proportional to orbital radius cubed. |

kilogram | Unit of mass. |

kilowatt-hours | Energy transferred when 1000 Watts of power is used for 1 hour. |

kinetic energy (KE) | The energy gained when work is done on a body to increase its speed. |

Kirchhoff's 1st | sum of currents into junction = sum of currents out of junction |

Kirchhoff's 2nd | Around a closed loop, sum of EMF's = sum of PD's |

Large Hadron Collider (LHC) lasers | Particle accelerator at CERN |

Laser | A monochromatic, parallel source of light. |

latent heat | Heat required to change state. |

LCDs (liquid crystal displays) | Use polarisation to create images. |

length | distance between two points on an object |

length contraction | Reduction in length due to relative motion of object and observer. |

lenses | Used to bring light rays to / diverge them from a focal point. |

Lenz's law | Direction of induced current opposes change producing it. |

leptons | Fundamental particles with small mass. |

light | Visible part of EM spectrum. |

light bulbs | Convert electrical energy to light. |

light clocks | Imaginary timer used in relativity explanations. |

light dependent resistors (LDRs) | Semi conductor device whose resistance depends on light intensity. |

light years | Distance travelled by light in one year. |

linear | of the form y = mx +c |

linear accelerators | Accelerate charged particles in straight lines. |

linear equation | of the form y = mx +c |

linear magnification | Ratio size of image/size of object |

linearization | Rearranging an equation so it is in the form y = mx +c |

liquid crystals | Change polarisation plane unless a Pd is applied. |

liquids | No fixed shape but fixed volume. |

logarithmic scales | Divisions increase by a constant factor usually 10. |

longitudinal waves | Disturbance in the same direction as propagation. |

Lorentz transforms | Transformations that take into account the constant velocity of light. |

Loudness | Related to amplitude |

luminosity | Total power radiated by a star. |

magnetic fields | Region of space where a small magnetic dipole experiences a turning force. |

magnetic north | End of a magnet that points north |

magnetic resonance imaging (MRI) magnets | Uses oscillations of nuclei in magnetic fields to form medical images. |

magnetic south | End of magnet that points south |

Malus's law | Intenity of polarised light is proportional to the square of the cosine of difference in plane of polarisation |

mass - energy equivalence | E = mc^2 |

mass defect | Mass of pparts - mass of nucleus |

mass spectrometers | Separate nuclei according to mass. |

measurement uncertainty | the uncertainty of the instrument and how it is used |

meltdown | Result of a nuclear reactor overheating. |

mesons | A particle made of two quarks |

metre (unit) | Si unit of length |

Michelson‚Morley experiment | Showed that the speed of light was not affected by motion relative to it's medium. |

microwaves | EM radiation with wavelegth of the order of mm. |

Milky Way | Our galaxy. |

Millikan photoelectric experiment | Uses stopping potential to measure KE of photo electrons. |

moderator | Used to slow down neutrons so they ate absorbed more easily e.g. Graphite |

molecules | Atoms held together by the interatomic force. |

molecules excitation | Increasing the KE of molecules. |

momentum | mass x velocity |

muons | A fundamental particle in the lepton family. |

natural frequency | Frequency of an oscillating system with no driving force. |

negative acceleration | change of velocity in a negative direction |

negative time | Before the clock started. |

negative work | If you do negative work you gain energy. |

neutral currents | Particle interactions with no exchange of charge. |

neutrinos | A group of fundamental particles with no charge and very small mass. |

neutron stars | Dense stars made of neutrons. |

neutrons | Neutral particles made of 3 quarks. Part of the nucleus. |

newton (unit) | SI unit of force. |

Newton's 1st | A body remains at rest or with constant velocity unless acted upon by an unbalanced force. |

Newton's 2nd law | F = ma |

Newton's 2nd law (momentm) | The rate of change of momentum of a body is directly proportional to the unbalanced force acting on that body and takes place in the same direction. |

Newton's 3rd Law | If body A exerts a force on body B then body B will exert and equal and opposite force on body A. |

Newton's laws of motion | 3 laws that relate force and motion. |

Newton's model | A static model of the universe. |

Newton's universal law of gravitation | All point masses attract all others with a force that is proportional to the product of their mass and inversley proportional to their separation squared. |

nodes | Points on a standing wave with zero amplitude. |

non-ohmic conductors | Conductors where current is not proportional to voltage |

normal force | The force perpendicular to two surfaces in contact |

nuclear fission | The splitting up of large nuclei |

nuclear force | The force between nucleons |

nuclear fuels | Fissile material used in nuclear reactors |

nuclear fusion | The joining of small nuclei |

nuclear magnetic resonance (NMR) | Using the vibration of nuclei in magnetic fields to produce medical images |

nuclear radiation | Particles emitted by unstable nuclei |

nuclear waste | The remaining material after fission |

nuclei (atoms) | Heavy centre of an atom |

nucleons | Protons and neutrons |

nuclides | Different nuclear forms. |

observers | Experimenters committed to make measurements in a given frame of reference |

Occam's razor | Simple is best |

ohm (unit) | Unit of resistance |

Ohm's law | Current is proportional to voltage |

ohmic conductors | Materials that obey Ohm's law |

oil-fired power stations | Use oil to produce electricity |

open universe | A model of the universe with continuous expansion |

Oppenheimer‚Volkoff limit | The minimum size for the formation of a black hole |

optical fibres | Thin fibres that transmit light by total internal reflection |

orbits | e.g. The moon orbits the Earth, entripetal force provided by gravity |

oscillating water columns | Convert wave power into electricity |

oscillation | A repeating cycle |

oscillations amplitude | Maximum displacement from equilibrium position |

outliers (graphs) | Points that don't lie on the best fit line |

pair production | Particle anti-particle pairs formed from photons |

parabolic paths | The trajectory of a projectile |

parallax | Shift of objects due to movement of observer |

parallel circuits | Components connected between the same points |

parsecs | Distance between stars that subtends an angle of one arcsecond |

particle accelerators | Devices that accelerate charged particles |

particle detectors | Devices that detect particles e.g. Geiger tube |

particle model | Model that describes matter as being made of particles |

Pauli exclusion principle | Particles with spin half can not occupy the same energy state |

Peak current and Voltage | Maximum values. |

pelamises | A device that converts wave power into electricity |

pendulums | Small bodies suspended on strings |

percentage uncertainties | Uncertainty divided by value as a percent |

permittivity (electric fields) | Constant relating electric force with charge |

phase angle | Angular difference between two oscillating bodies |

phase difference | Angular difference between two oscillating bodies |

photo gates | Devices used for measuring time elapsed |

photodiodes | Semi conducting devices that convert light into electricity |

photoelectric effect | Emission of electrons due to absorption of light |

photons | Particles of light |

photosynthesis | Conversion of carbon dioxide and water into carbohydrates in plants using energy from the sun. |

photovoltaic cells | Semi conducting devices that convert light into electricity |

pions | Particles made of two quarks part of the meson family |

pitch (sound) | Perception of frequency of sound |

planar wavefronts | Waves propagating in parallel lines |

Planck's constant | Constant relating photon energy and frequency |

planets | Large bodies orbiting the sun |

plasmas | Gases made up of ions |

plum pudding model (atoms) plutonium | Rutherford's model of the atom |

polar satellites | Satellites that orbit the poles |

polarization | Restricting the disturbance of a wave to one plane |

positive acceleration | change of velocity in a positive direction |

positive work | If you do positive work you lose energy |

positrons | The anti particle of electrons |

potential difference (p.d.) | The work done per unit charge in moving a small positive test charge between two points |

potential dividers | Series resistors used to produce a variable potential difference |

potential energy (PE) | The work done in placing a body in a position |

potential gradient | change in V / change in x |

potential wells | A minimum in potential energy |

Pound‚Rebka experiment | Measured the change in frequency when EM radiation travelled vertically |

power | Energy per unit time |

power lines | Cables used to trsnsmit electrical energy |

power loss (electricity) | Energy loss in power lines. |

power stations | Generate electrical energy. |

precise measurements | close to each other |

pressure | Force per unit area |

primary colours | Red, green, blue |

probability function | Function that gives the probability of the position of a particle |

probability waves | A wave function that gives the probability of the position of a particle |

projectile motion | Motion of a particle moving freely in a uniform gravitational field |

proper length | The length of an object measured by an observer at rest relative to it |

proper time | The time of an event measured by a clock at rest relative to the event |

proportional relationship | of the form y = mx |

proton-proton chains | The process of fusion producing energy in the sun |

protons | Positive particles made of three quarks present in the nucleus |

protostars | The early stage in the life of a star |

pupil | apperture of the eye |

PV diagrams | Pressure-volume graphs |

Pythagoras' theorem | Square of hypotenuse is equal to the sum of the square of the other two sides |

quantized energy | For example electrons can only exist in certain energy levels |

quantum chromodynamics (QCD) | The theory explaining the force between quarks |

quantum model | Atomic model describing the electron energies in terms of a probability function |

quantum numbers | Numbers defining electron energy states |

quantum tunneling | A particle can get past a barrier without climbing over it. |

quark confinement | The reason why quarks can not exist alone |

quarks | Fundamental particles that make up baryons and mesons |

radians | Measurement of angle. Arc length divided by radius |

radiation | Transfer of heat via electromagnetic waves. |

radiation absorption spectra | Produced when white light is passed through a low pressure gas |

radiation therapy | Using radioactive isotopes to kill cancer cells |

radiation-dominated universe | A time when universe was dominated by photons |

radio waves | Long-wavelength EM radiation |

radioactive dating | A way of using the decay of radioactive isotopes to determine age |

radioactive isotopes | Nuclei with the same proton number different neutron number. |

random errors | errors resulting from uncertainties in measuring device or conditions. |

range | horizontal distance travelled by projectile |

rate of change | dx/dt |

Rayleigh criterion | Two objects are resolved if the first minimum in the diffraction pattern of one coincides with the principal maxima of the other |

rays (waves) | Lines drawn at right angles to wavefronts |

real images | Points where rays cross |

red giants | Stars at the end of their life cycle |

red shift | Shift in wavelength due to the recession of sources of light |

reflection | What happens when light hits a mirror |

refraction | Change of direction of a wave when passing through a boundary between two media |

refractive indices | Sine of the angle of instance over angle of refraction |

refrigerators | Use thermic cycles to transfer energy from hot bodies to cold |

relative atomic mass | The mass of an atom relative to 1/12 the mass of a carbon 12 atom |

relative velocity | The velocity measured by a moving observer |

resistance | The ratio of potential difference / current |

resistivity | The resistance of a cubic meter of material |

resistors | Devices that reduce the current in a circuit |

resolution | The ability to distinguish two point objects |

resolvance | The ability to resolve spectral lines |

resonance | When an oscillating system is made to vibrate at its own natural frequency |

resonance curves | A graph of amplitude against forcing frequency |

resultant force | The vector sum of all forces acting on a body |

retina | light sensitive part of the eye |

right hand grip rule | thumb in direction of current fingers curl in direction of field |

root mean square current and voltage (rms) | The root of the mean of the squares. Gives same power as DC value |

rotation | Caused when a force does not act through the centre of mass |

Rutherford model | Plum pudding model |

sampling | The rate of taking measurements by a digital device |

Sankey diagrams | Flow diagrams |

satellites | Bodies that orbid the earth |

scalars | Quantities with magnitude but no direction |

second law | In any interaction the entropy will always increase |

seconds (time) | SI unit of time |

serendipity | Luck |

series circuits | Components connected in a line |

SHM KE | Max at equilibrium position |

SHM PE | Max at max displacement |

SHM toal energy | Constant = PE + KE |

SI units | International system of units |

sig figs in uncertainty | 1 or 2 |

simple harmonic motion (SHM) | When force is proportional to displacement from a fixed point and always acts towards that point |

simultaneity | Events taking place at the same time are not at the same time for all observers |

small angle approx. | SinA = A in radians |

Snell's law | Sine angle of incidence / Sine angle of refraction = Constant |

solar constant | Intensity of solar radiation incident at the earth |

solar energy | Using energy from the sun to produce electricity |

solenoids | Coils where the windings are side by side |

sonic boom | A bang caused by the accumulation of sound when a body travels at the speed of sound. |

sonometer | A single stringed musical instrument. |

sound | propagation of changes in pressure. |

special relativity | The study of relativity applied to inertial frames of reference. |

specific energy | enrgy/mass |

specific heat capacity | The amount of heat required to raise the temperature of 1kg of a substance by 1 K. |

specific latent heat (see latent heat) | The amount of heat required to change the state of 1 kg of a substance without change in temperature. |

spectrometer | A device used to view spectra |

Spectrum of light | Ranges from red (low frequency long wavelength) to blue (high frequency, short wavelength) |

speed | Distance travelled / time |

speed of light in a vacuum | c = 300,000,000 m/s |

spherical aberration | The outer rays passing through a convex lens are deviated more than the inner ones. |

spin | A propety of particles, can be 1/2, 1 or 0. can align or not align 1/2 + 1/2 = 1 or 0 |

spin (particles) | A property of all subatomic particles |

spring constant | Force/extension |

standing waves | Formed when a wave interferes with its reflection. |

states of matter | solid, liquid and gas |

Stefan‚Boltzmann law | Radiated power per unit area is proportional to thhe 4th power of absolute temperature |

stellar clusters | Groups of stars. |

step indexed fibres | Optical fibres made of layers with decreasing refractive index. |

stimulated emission | When the emmission of a photon is initiated by a photon on the same frequency. |

stopping (lenses) | Applying a small aperture to a lens to reduce spherical abberation. |

straight line graphs | y = mx + c |

strangeness | A property of subatomic particles expressed as a quantum number. |

stringed instruments | instruments with stretched strings e.g. Guitar |

strong force/interactions | The force between quarks. |

subsidiary maxima | Small maxima between pricipal maxima. (number of slits - 2) |

supernovas | Exploding stars. |

superposition | Vector addition of wave displacement |

suvat 1 (uvat) | a =(v - u)/t |

suvat 2 (suvt) | s = (u + v)t/2 |

suvat 3 (suat) | s =ut + at^2/2 |

suvat 4 (suva) | v^2 = u^2 + 2as |

suvat equations | A set of equations used to solve problems involving motion with constant acceleration. |

systematic errors | When the same error occurs in all measurements. |

temperature | Defines the direction of heat flow. Related to average KE of molecules. |

tension | When a force is applied via a string. |

tesla (unit) | Unit of magnetic flux density. |

thermal | Refers to systems where there is exchange of heat. |

thermal capacity | The amount of heat required to raise the temperature of a body by 1 K. |

thermal equilibrium | When there is no flow of heat between two bodies in contact. |

thermodynamic cycles | A series of transformations that begin and end at the same state. |

threshold frequency | The minimum frequency require for the emission of photo electrons. |

tidal power | Electrical energy generated from the flow of tides. |

time period | time for one revolution |

total internal reflection | occurs when light is incident on a boundary to a less dense medium. |

totally inelastic collisions | When bodies stick together. |

trajectory | path of a particle |

transformers | Coils with shared magnetic field. Np/Ns = Vp/Vs |

translational equilibrium | When the forces acting on a body add uo to give zero. |

transmutations | When a nucleus changes to another |

transverse waves | When the direction of disturbance is perpendicular to the direction of propagation. |

turbine | Creates rotation from the KE in moving fluids. |

twin paradox | One twin takes a high speed journey and returns to Earth younger |

ultrasound | High frequency, inaudible sound. |

ultraviolet (UV) light uncertainty | High freqency EM radiation, just outside the visible spectrum. |

uncertainty | How well you can define a quantity. |

uncertainty in a range of values | (max-min)/2 |

unified mass units | 1/12 of the mass of a carbon 12 atom. |

uniform electric field strength | E=V/d |

uniform fields | Parallel, equally spaced field lines. |

unstable nuclei | Nuclei that emit radiation changing into something with higher BE. |

upthrust | Same as buoyancy. |

variable stars | Stars with varying brightness. |

vector addition | nose to tail, resultant is line joining free nose to tail. |

vectors | Quantities with magnitude and direction e.g. Force |

velocity | Displacement / time |

velocity‚time graphs | Linear when acceleration is constant. |

vernier caliper | A sliding scale used to measure small lengths accurately |

vertical component (angle A measured to horizontal) | FsinA |

vertical motion (projectile) | constant negative acceleration |

Video analysis | Using LoggerPro to analyse motion in a video. |

volt (unit) | Unit of potential. Same as J/C |

voltmeters | Instrument for measuring PD. Ideally have infinite resistance. |

volume of a cube | L^3 |

volume of a sphere | 4/3 πr^3 |

W boson | Exchange particle in weak interactions |

watt (unit) | SI unit of power J/s |

wave particle duality | The theory that the position of particles given by a wave function. |

wave speed | frequency x wavelength |

wavefronts | Lines joining points on a wave that are in phase. |

wavelength | The distance between two consecutive, in phase points on a wave. |

waves | A physical phenomenon that diffracts and interferes |

weak force/interactions | Interactions involving neutrinos |

weight (gravitational force) | Force of attraction between a body and the Earth. |

weightlessness | Apparent lack of weight in free falling frames of reference. |

white dwarves | Small hot stars. After the main sequence. |

white light | a mixture of all the colours in he rainbow. |

Wien's law | The peak wavelength in the black body spectrum is inversely proportional to absolue temperature. |

wind instruments | Make use of standing waves in pipes. |

wind turbines | Convert KE in wind into electrical energy. |

wire chambers | A particle detector. |

work (energy transfer) | Force x distance moved in direction of force. |

work function (photoelectric effect) | Minimum energy required to liberate photo electrons. |

X-rays | High frequency EM radiation. |

X-rays diffraction | The result of passing X-rays through crystals. |

y intercept | Where a line crosses the y axis- |

zinc plate experiment | A demonstration of the photoelectric effect. |

zinc sulphide | A material used in the screens of electron tubes. |