Absolute uncertainty - a quantity giving the extremes a measured value falls within

Absolute zero - the temperature at which all random motion of molecules stops

Absorption spectra - the set of wavelengths of photons absorbed by a substance

Ac generator - a rotating coil in a magnetic field that generates ac voltage

Acceleration of free fall - the acceleration due to the pull of the Earth on a body

Accurate - a measurements where the systematic error is small and so close to the ‘true’ value

Activity - the rate of decay of a radioactive sample

Albedo - the ratio of scattered to incident intensity of radiation

Alpha decay - a decay producing an alpha particle

Alpha particle - the nucleus of helium-4

Alternating current (ac) - current in which electrons oscillate instead of moving with same drift speed in the same direction

Alternating voltage - voltage that takes positive as well as negative values

Ammeter - an instrument that measures the electric current through it

Amplitude - the largest value of the displacement from equilibrium of an oscillation

Angular frequency - same as angular speed

 - the product of mass, speed and orbit radius of a particle

Angular separation - the angle that the distance between two objects subtends at the observer’s eye

Angular speed - the ratio of angle turned to time taken

Aniontons’ law or Gay-Lussac’s law - the relation between pressure and temperature of a fixed quantity of an ideal gas when the volume is kept constant

Anti-particle - a particle with the same mass as its particle but with all other properties opposite, such as electric charge

Antinode - a point in a medium with a standing wave where the displacement is momentarily a maximum

Atmosphere - a non-SI unit of pressure

Atomic (or proton) number - the number of protons in a nucleus

Atomic mass - the mass of an atom measured in units of u

Atomic mass unit - a unit of mass equal to of the mass of a neutral atom of carbon-12

Average - another word for mean

Average power - for sinusoidally varying voltages and currents the average power in a conductor is half the peak value

Average speed - the ratio of distance travelled to total time taken

Average velocity - the ratio of displacement to total time taken

Avogadro constant - the number of particles in one mole

Background radiation - radiation from natural sources

Bar magnet - a rectangular piece of iron that has a magnetic field

Baryon - a particle made up of three quarks

Baryon number - a conserved quantum number j it is assigned to each quark and by extension to baryons

Battery - a source of emf

Best estimate - the average value of a set of measurements of a given quantity that will serve as the quoted value for that quantity

Beta minus decay - a decay producing an electron and an anti-neutrino

Beta particle - an electron

Beta plus decay - a decay producing a positron and a neutrino

Binding energy - the minimum energy that must be supplied to completely separate the nucleons in a nucleus or the energy released when a nucleus is assembled

Black body - a theoretical body that reflects none of the radiation incident on it and so absorbs all of it

Blue-shift - an decrease in the observed wavelength

Boiling - the change from the liquid to the vapour state at a specific constant temperature

Bottom - a flavour of quark with electric charge but heavier than the strange quark

Boyle’s law - the relation between pressure and volume of a fixed quantity of an ideal gas when the temperature is kept constant

Capacitance - the charge that can be stored on a capacitor per unit voltage

Capacitor - a device that can store electric charge

Carbon brushes - conducting, soft material that joins the slip rings to the external circuit in an ac generator

Centripetal acceleration - the acceleration due to a changing direction of velocity

Centripetal force - a force pointing to the centre of a circular path

Chain reaction - a self-sustaining reaction

Charge carrier - charged panic les that are able to move, creating an electric cm rent

Charge polarisation - the separation of charge when a dielectric is exposed to an external electric field

Charles law - the relation between volume and temperature of a fixed quantity of an ideal gas when the pressure is kept constant

Charm - a flavour of quark with electric charge +2/3e, but heavier than the up quark

Circular slit - an opening in the shape of a circle through which diffraction takes place

Coefficient of dynamic friction - the ratio of the force of friction to the normal reaction force on a body while the body is sliding on a surface

Coefficient of static friction - the ratio of the maximum force of friction that can develop between two bodies to the normal reaction force on a body while the body is at rest

Coherent - sources whose phase difference is constant in time compression a point in a medium through which a wave is travelling that has maximum density

Condensation - the change from the vapour to the liquid state

Conduction - the transfer of heat through electron and molecular collisions

Conductor - an object or material through which electric current can pass

Conservation of energy - the principle that energy cannot be destroyed or created but can only be changed from one form into another

Conservation of momentum - when the net force on a system is zero, the total momentum of the system is constant

Conservative forces - forces for which work done is independent of the path followed

Conserved - a quantity that stays the same before and after an interaction

Constructive interference - the superposition of two identical waves that arrive at a point in phase

Contact force - another name for a reaction force

Control rod - a rod that regulates the rate of energy release in a nuclear fission reactor by regulating the absorption of neutrons

Convection - the transfer of heat in fluids through differences in fluid density

Convection current - motion of a fluid as result of differences in fluid density

Convection current - motion of a fluid as result of differences in fluid density

Coulomb’s law - the electric force between two point charges is proportional to the product of the charges and inversely proportional to the square of their separation

Crest - point on a wave of maximum displacement

Critical angle - the angle of incidence for which the angle оf refraction is a right angle

Critical mass - the smallest mass of fissionable material that can sustain fission reactions

Decay constant - the probability per unit time for a nucleus to decay

Decay series - the sequence of decays that occurs until a radioactive element reaches a stable nuclide

Destructive interference - the superposition of two identical waves that arrive at a point 180° out of phase

Dielectric - insulator that shows charge polarisation

Diffraction - the spreading of a wave past an aperture or an obstacle

Diffraction grating - a series of very many and very narrow slits

Diode - a device that lets current through it only in one direction

Diode bridge rectifier - a circuit that achieves full-wave rectification

Dipole - a pair of two equal and opposite electric charges

Direct current (dc) - current in which electrons move in the same direction with the same average drift speed

Discrete - energy that can take a set of specific values as opposed to a continuous range of values

Dispersion - the dependence of refractive index on wavelength

Displacement - the change in position; for an oscillation, the difference between the position of a particle and its equilibrium position

Distance - the length of the path followed by a particle or object

Distance of closest approach - the smallest distance between an incoming particle and the target in a scattering experiment

Doppler effect - the change in measured frequency when there is relative motion between source and observer down a flavour of quark with electric charge

Drag force - a force of resistance to motion

Dynamic or kinetic friction - a force opposing motion when a body moves

Eddy currents - small induced currents in a conductor where the flux is changing that dissipate energy

Efficiency - the ratio of useful work or power to input work or power

Elastic potential energy - the energy stored in a spring when it is compressed or stretched

Electric charge - a conserved property ot matter

Electric field - the field produced by electric charges

Electric field strength - the electric force per unit charge experienced by a small point positive charge

Electric potential - the work done per unit charge by an external agent in bringing a small point positive charge from infinity to a point

Electric potential energy - the work that needs to be done by an external agent in order to bring a set oi charges horn where they were separated by an infinite distance to their current position

Electric resistance - the ratio of the voltage across a device to the current through it

Electrical energy - same as electric potential energy

Electromagnetic - an interaction mediated by the exchange of photons

Electromagnetic waves - transverse waves moving at the speed of light in vacuum consisting of oscillating electric and magnetic fields at right angles to each other

Electroweak interaction - the interaction that is the unification of the electromagnetic and the weak nuclear interactions

Elementary particles - particles that have no consituents

Emf - the work done per unit charge in moving charge across the terminals of a battery

Emission spectrum - the set of wavelengths of photons radiated by a substance

Emissivity - the ratio of the intensity radiated by a body to the intensity radiated by a black body of the same temperature

Energy - something that can be stored and which can be used in order to do things

Energy balance equation - an equation expressing the equality of incoming and outgoing intensities of radiation

Energy density - the energy that can be obtained from a unit volume of fuel

Energy level diagram - a diagram showing the discrete energies a system can take

Equation of state - the equation relating pressure, volume, temperature and number of moles of a gas

Equilibrium - the state when the net force on a system is zero

Equipotential surfaces - set of points that have the same potential

Error bar - the representation of absolute uncertainty in a graph of plotted points

Escape velocity - the minimum speed at launch so that a particle can move to infinity and never return

Exchange particle - an elementary particle used as the intermediary of an interaction

Excited state - a state of energy' higher than the ground state energy

Expanding universe - the distance between distant galaxies is increasing as space between them stretches

Expansion - another name for rarefaction

Family lepton number - a quantum number assigned to each lepton in each family

Faraday’s law - the induced emf in a loop is the rate of change of magnetic flux linkage through the loop

Feynman diagram - a pictorial representation of an interaction

First harmonic - the mode of vibration of a standing of wave lowest frequency

Flavour - a type of quark

Fluid resistance force - a force of resistance to motion when a body moves through a fluid

Flux linkage - the magnetic flux in a loop times the number of turns in the loop

Force - something that accelerates a body

Force of reaction - a force that develops as a result of two bodies being in contact

Force pair - the combination of two forces that are applied to one absolutely solid body and at the same time are equal in magnitude and opposite in direction

Fractional uncertainty - the ratio of the absolute unceirtanty to the mean value of a quantity

Free-body diagram - a diagram showing a body in isolation with all forces acting on it drawn as arrows

Freezing - the change from the liquid to the solid state at a specific constant temperature

Freguency - the number of full oscillations or waves it time

Friction laws - empirical ‘laws’ about frictional forces

Fuel - a source of energy

Fuel rods - containers of nuclear fuels, e.g. oxides of uranium-235 r plutonium-239, in nuclear fission reactor

Full-wave rectification - the turning of ac current into dc current during both halves of the cycle

Fundamental unit - in the SI system, the kilogram, metre, second, kelvin, mole, ampere and candela arc fundamental units; all other units arc combinations of these and are called derived units

Gamma decay - a decay producing a gamma ray photon

Gamma ray - a photon

Gay-Lussac’s law or Amontons’ law - the relation between pressure and temperature of a fixed quantity of an ideal gas when the volume is kept constant

Gravitational field - the field produced by mass; its strength is the gravitational force per unit mass experienced by a small point mass

Gravitational field strength - the gravitational force per unit mass experienced by a small point mass

Gravitational interaction - an interaction mediated by the exchange of gravitons

Gravitational potential - the work done per unit mass by an external agent in bringing a small point mass from infinity to a point

Gravitational potential energy - the work that must be performed by an external agent to raise a mass to certain height from a position where the height is zero, or to bring a set of masses to their current position from when they were separated by an infinite distance

Greenhouse effect - the phenomenon in which infrared radiation emitted by the Earth’s surface is absorbed by greenhouse gases in the atmosphere and then re-radiated in many directions, including back down to Earth

Greenhouse gas  - a gas in the atmosphere that absorbs infrared radiation

Ground state - the state of lowest energy

Hadron - a particle made up of quaks

Half-life - the time for the activity of a radioactive sample to be reduced to half  its initial value

Half-wave rectification - the turning of a current into dc current by allowing the passage of current during one half of the cycle only

Heat - the energy transferred as a result of a temperature difference

Heat exchanger - system of extracts thermal energyfrom the moderation of a nuclear reactor

Higgs particle - the particle whose interactions with other particles gives mass to those particles

Hooke’s law - the tension in a spring is proportional to the extension or compression

Hydroelectric power - plant producing power by converting the potential or kinetic energy of water

Ideal gas - an idealised version of a gas obeying the gas laws at all pressures, volumes and temperatures

Impulse - the product of force and the time interval for which the force acts; it equals the change in momentum

Inertia - the tendency of a massive body to remain in its current state of motion

Instantaneous speed - the speed at an instant of time; the rate of change of distance with time

Instantaneous velocity - the velocity at an instant of time; the rate of change of displacement with time

Insulator - an object or material which electric current cannot pass through

Intensity - power of radiation per unit area; power per unit

Interaction vertex - a building block of Feynman diagrams representing a fundamental interaction process

Internal energy - the total random kinetic energy and interrnole cular potential energy of the molecules of a substance

Inverse  square  law - a law where a physical quantity is inversely proportional to the square  of the  distance  from the source of that quantity; intensity of light from a source obeys an inverse square law

Ionizing - the ability to knock  electrons off atoms

Isolated - a system whose total energy stays constant

Isotopes - nuclei of the same element containing the same number of protons but different numbers of neutrons

Kinetic energy - the energy a body has as a result of its motion

 Kirchhoff's loop law - ΣV=0

Kirchhoff’s current law - ΣI_n=ΣI_out

Lenzs law - the direction of the induced emf is such as to oppose the change in flux that created it

Lepton - an elementary particle

Linear momentum - the product of mass and velocity

Longitudinal wave - a wave where the displacement is parallel to the direction of energy transfer

Magnetic field - a field created by electric currents and moving charges

Magnetic field lines - imaginary curves whose tangents give the magnetic field

Magnetic flux - the product of the component of the magnetic field strength normal to an area

Magnetic flux density - another name for the magnetic field strength B; it is the force per unit charge on a charge moving with unit velocity at right angles to the field body is put into a liquid in a calorimeter

Magnetic force the force experienced by a magnetic field on a moving charge or an electric current

Magnetic hysteresis - the lagging of an effect behind its cause, as when the change in magnetism of a body lags behind changes in the magnetic field

Magnitude - the length of a vector; the size of a quantity

Mains’s law - the transmitted intensity of polarised light through a polariser is reduced by a factor of cos’8

Mass (or nucleon) number - the number of protons plus neutrons in a nucleus

Mass defect - the difference in mass between the mass of the nucleons making up a nucleus and the nuclear mass

Mean - the sum of a set of measurements divided by the number of measurements

Mean value - the average value of a set of measurements of a given quantity that will serve as the quoted value for that quantity

Melting - the change from the solid to the liquid state at a specific constant temperature

Meson - a particle made up of one quark and one anti-quark

Method of mixtures - a method to measure specific heat square of the amplitude of the wave

Moderator - body whose molecules slow down the fast neutrons produced in a fission reaction through collisions with the neutrons

Modulated - the change in the two-slit intensity pattern when the single-slit diffraction elTect is taken into account

Molar mass - the mass of one mole of a substance

Mole - a quantity of a substance containing as many particles as atoms in 12 g of carbon-12

Net force - the one force whose effect is the same as that of a number of forces combined

Neutrino - a neutral particle with very small mass that interacts very weakly

Newton’s first law - particle moves with a constant velocity (which may be zero) when no forces act on it

Newton’s law of gravitation - there is a force of attraction between any two point masses that is proportional to the product of the masses and inversely proportional to the square of their separation; the force is directed along the line joining the two masses

Newton’s second law - the net force on a body is the rate of change of the body’s momentum

Newton’s third law - when a body A exerts a force on body B, body B will exert an equal but opposite force on body A

Node - a point in a medium with a standing wave where the displacement is always zero

Non-renewable - sources of energy that are being used at a much faster rate than that at which they are being produced and so will run out

Notional emf - the emf generated when a conductor moves in a region of magnetic field

Nuclear fission - the reaction in which a heavy nucleus splits into two medium-sized nuclei plus neutrons, releasing energy

Nuclear fusion - the reaction in which  two light  nuclei join to form a heavier nucleus, releasing energy nucleon a proton or neutron

Nuclide - a nucleus with a specific number of neutrons and protons

Ohm’s law - at constant temperature the current through most metallic conductors is proportional to the voltage across the conductor

Order of magnitude - an estimate given as just a power of 10

Pair annihilation - the disappearance of a particle and its anti-particle when they collide

Pair creation - the production of a particle and its anti-particle from a vacuum

Parallel connection - resistors connected so that they have the same potential difference across them

Parallel plates - two parallel and equally but oppositely charged plates

Penetrating - the ability to move deep into a material

Period - the time needed to produce one full oscillation or wave

Periodic - motion that repeats

Permittivity of vacuum - the constant s appearing in Coulomb's law when the charges are situated in a vacuum

Phase - the state of a substance depending on the separation of its molecules; we consider the solid, liquid and vapour phase in this course

Phase change - the phase of a wave increases by π (radians) upon reflection from a medium of higher refractive index

Phase difference - the quantium  shift/period*360 or  shift/waveleght*360 

Photo-surface - a metallic surface that ejects electrons when electromagnetic radiation is incident on it

Photoelectric effect - the phenomenon in which electromagnetic radiation incident on a metallic surface forces electrons to move from the surface

Photon - the particle of light, a quantum of energy

Photovoltaic cell - a device that converts solar energy into electrical energy

Plane polarized - light whose electric field oscillates on one plane

Point particle - a particle that is assumed to be a mathematical point

Polariser - a device such that light passing through it emerges polarised

Position - generally a vector from some origin to the place where a particle is situated

Positron - the anti-particle of the electron travelling that has minimum density

Potential difference - the work done per unit charge in moving a small point positive charge between two points

Potential energy - the energy a system has as a result of its state

Power - the rate at which work is being done or energy is being dissipated

Precise - measurements where the random error is small

Pressure - the normal force on an area per unit area

Primary cell - a source of emf that, once discharged, has to be discarded

Primary energy - energy that has not being processed in any way

Pulse - an isolated disturbance in a medium carrying energy and momentum

Pumped storage system - plant in which water is pumped back up to higher elevations during off-peak hours so that it can again be released later during periods of high demand for electricity

Quantised - a quantity that can take on a discrete set of values

Quantised energy - energy that takes values from a set of values that are not continuous

Quantised energy - energy that takes values from a set of values that are not continuous

Quantum - a unit of something, for example, energy

Quark - an elementary particle making up nucleons (and hadrons) appearing in six flavours

Quark confinement - the principle that free quarks cannot be observed

Radial - the direction towards or away from the centre of a spherical body

Radiation - energy in the form of electromagnetic waves

Radioactivity - the phenomenon in which nuclei emit

Random uncertainty - an error due to inexperience of the observer and the difficulty of reading instruments

Rarefaction - a point in a medium through which a wave is travelling that has minimum density

Ray - the direction of energy transfer of a wave

Rayleigh criterion - the condition for resolving  two objects; resolution is possible when the central maximum in the diffraction pattern of one source coincides with the first minimum of the diffraction pattern of the other real gas a gas obeying the gas laws approximately for limited ranges of pressures, volumes and temperatures

Red-shift - an increase in the observed wavelength

Reflection - the scattering of radiation off a surface such that the angle of incidence is equal to the angle of reflection

Refraction - the change in speed of a wave as it enters another medium and the subsequent change of direction (except at normal incidence)

Refractive index - the ratio of the speed of light in vacuum to the speed of light in a material

Renewable - sources of energy from a source that has, for all practical purposes, an infinite lifetime

Resistivity - the resistance of a conductor of unit length and unit cross-sectional area

Resolution - the ability to see as distinct two objects that are distinct

Resolving power - the ability of a diffraction grating to see as distinct two wavelengths that are close to each other

Restoring force - a force directed towards the equilibrium position of a system

Right-hand grip rules - the right-hand grip rule for a current-carrying wire gives the direction of the magnetic field due to the current in a wire; the right-hand grip rule for a solenoid gives the direction of the magnetic field due to the current in a solenoid; the right-hand rule gives the direction of the magnetic force on a moving charge

Root mean square (rms) - value of a current or a voltage that would give the same average power dissipation in a dc circuit component as in the ac circuit

Sankey diagram - a pictorial way to represent energy losses and transfers

Scalar - a quantity that has magnitude but no direction

Schrodinger theory - the theory that determines the wave function of a system

Schwarzschild radius - the distance from the centre of a star where the escape speed is the speed of light

Secondary cell - a rechargeable source of emf

Secondary energy - energy that has been processed in some way so as to make it useful

Series connection - resistances connected one after the other so they take the same current

Simple harmonic motion (SHM) - oscillatory motion in which the acceleration is opposite and proportional to displacement from equilibrium

Simple pendulum - a small mass attached to a fixed length of string that oscillates

Slip rings - conducting rings used to connect the rotating coil of a generator to the external circuit so that ac current is delivered to it

Snell’s law - the law relating the angles of incidence and refraction to the speeds of the wave in two media

Solar constant - the intensity of the Sun’s radiation at the position of the Earth’s orbit

Solenoid - a long, tightly wound coil

Specific energy - the energy that can be obtained from a unit mass of fuel

Specific heat capacity - the energy required to raise the temperature of a unit mass by one degree

Specific latent heat of fusion - the energy needed to change a unit mass from the solid to the liquid phase at constant temperature

Specific latent heat of vaporization - the energy needed to change a unit mass from the liquid to the vapour phase at constant temperature

Standard deviation - a measure of the spread of a set of measurements around the mean

Standard Model - the presently accepted model of elementary particles and interactions for quarks and leptons be reduced by repeated measurements

Standing wave - a wave formed from the superposition of two identical travelling waves moving in opposite directions

State of a gas - a gas with a specific value of pressure, volume, temperature and number of moles

Static friction - a force opposing the tendency to motion when a body is at rest

Stefan—Boltzmann law - the power radiated by a black body is proportional to the body's surface area and the fourth power of its kelvin temperature;  P = σT ⁴

Stopping voltage - the voltage in a photoelectric experiment that makes the photocurrent zero

Strange – a flavour of quark with electric charge -1/3e, but heavier than the down quark

Strong nuclear interaction - an interaction mediated by the exchange of gluons

Superposition - the displacement when two waves meet is the sure of the individual displacements

Systematic error - an error due to incorrectly calibrated wave function of a system instrument –n   is the same for all data points and cannot

Temperature - a measure of the ‘coldness’ or ‘hotness' ; the absolute temperature is a measure of the average random kinetic energy of the particles of a substance

Tension - the force developed in a string or spring as a  result of stretching and compressing

Terminal speed - the eventual constant speed attained by a body experiencing a speed-dependent resistance force

Thermal equilibrium - the state in which the temperature remains constant

Thermistor - a resistor whose resistance varies strongly with temperature

Thin film interference - a type of interference caused by reflected rays from the two boundaries of a thin film

Thomson model - an early model of the atom as a positive sphere of positive charge with electrons moving about in the sphere

Time constant - the time after which the charge on a discharging capacitor is reduced to about 37% of its original value

Top - a flavour of quark with electric  charge +2/3e , but heavier than the charm

Total internal reflection - when the angle of incidence is greater than the critical angle, the incident ray only reflects with no refracted ray

Total mechanical energy - the sum of the kinetic energy gravitational potential energy and elastic potential energy of a body

Transfer of thermal energy - the transfer of energy from one body to another as a result of a temperature difference

Transformer - a device that takes a given ac voltage as input and delivers a higher or lower ac voltage

Transition - the change from one energy level to another with the associated release or absorption of energy

Transverse wave - a wave where the displacement is at right angles to the direction of energy transfer

Trough - a point on a wave of minimum displacement

Tunnelling - the ability of subatomic particles to move into regions forbidden by energy conservation