Physics A Level AQA

Acceleration

change in v per unit t

Acceleration of free fall

Acceleration of an object only acted on by force of gravity

Accurate

Measurement obtained using calibrated instruments correctly

Accuracy

How close to the true value

Alpha radiation

Particle consisting of 2 P's and 2 N's

Amplitude

Max displacement of oscillating particle from equilibrium position

Annihilation

Particle and antiparticle meet, destroy eachother and emit radiation

Antibaryon

Hadron w/ 3 quarks

Antimatter

Antiparticles with same quantum values but opposite charge to corresponding particles

Antinode

Fixed point on stationary wave where amplitude is maximum

Atomic number Z

Number of P's in atom nucleus

Baryon

Hadron w/ 3 quarks

Base units

Units that define the SI system:

Kg
Amp
S
M

Beta radiation

when B- or B+ particles are emitted following decay of a neutron-rich or proton-rich nucleus

Braking distance

Distance travelled by vehicle in time taken to stop

Breaking stress/Ultimate tensile stress

Tensile stress needed to break a solid material

Brittle

Snaps without bending or stretching when subject to stress

Centre of mass

Point through which a single force on the body has no turning affect

Charge carriers

Charged particles that move through substance when PD applied across it

Kirchoff's 1st Law

Current passing through 2 or more components in series is the same through each component

At a junction the total current in \= total current out

Kirchoff's 2 Law

2 or more components in series - total PD across all the components is \= to sum of the PD's across each component

Sum of emf's around complete loop \= sum of PD's around the loop

Coherent

Constant phase difference and same frequency

Conservation rules

Rule that:
Baryon no
Lepton no
Charge
Energy
Momentum

always conserved in interactions

When is strangeness conserved?

Strong interactions

How are strange particles created?

Strong interactions

How to strange particles decay?

Weak interactions

Couple

Pair of equal and opposite forces acting upon the same body but not along the same line

Critical angle

The angle of incidence of a light ray must exceed this angle for total internal reflection to occur

Critical temperature

Temperature at or below which a superconducting material has zero resistivity

Cycle

Interval for an oscillating particle from a certain displacement and velocity to the next time the particle has identical displacement and velocity

de Broglie hypothesis

Matter particles have a wave-like nature

de Broglie wavelength

Wavelength of a matter particle

deexcitation

process by which atom loses energy by photon emission as electron moves to lower energy level - inner shell

denisty

mass per unit volume for substance

diffraction

spreading out of waves that pass through gap or near edge

diffraction grating

plate with close parallel slits on it

dispersion

splitting of beam of white light into colours by prism

displacement

distance in a given direction from equilibrium position

drag force

force of fluid resistance on an object moving through fluid

ductile

stretches easily without breaking

efficiency

ratio of useful energy transferred to energy supplied to it

output power/input power

elastic limit

point beyond which wire is permanently stretched

elasticity

property of solid that allows it to regain shape after being deformed

electrolysis

process of electrical conduction in a solution or molten substance due to charged ions moving to oppositely charged electrode

electrolyte

solution that conducts electricity

electromagnetic interaction

force or interaction between 2 charged objects

electromagnetic wave

wavepacket or photon consisting of transverse electic and magnetic waves in phase and at right angle to eachother

emf

electrical energy per unit charge produced inside electrical source

electron volt

work done when an electron is moved through a PD of 1V

endoscope

optical fibre device used to see inside cavities

energy

capacity to do work

energy levels

discrete energy levels that electrons take in shells of atom

equilibrium

object in rest or constant motion

error bar

uncertainty representation on a graph

error of measurement

uncertainty of a measurement

excitation

process in which atom absorbs energy without becoming ionised when electron moves from inner shell to higher energy level in outer shell

first harmonic

pattern of stationary waves on a string when it oscillates at lowest possible frequency

fluroescence

emission of visible photons after atoms deexcite

frequency

number of cycles of a wave that pass a point per second

friction

force opposing the motion of a surface that moves or tries to move across another surface

gamma radiation

high energy photons emitted by unstable nuclei or produced in particle annihilations

gravitational field strength

force per unit mass on small object in gravitational field

ground state

lowest energy state of an atom

hadron

particles and anti that can interact through the strong interaction

Hooke's Law

the extension of a spring is proportional to the force applied to it

inertia

resistance of an object to a change of its motion

interference

formation of points of cancellation and reinforcement where two coherent waves pass through eachother

internal resistance

resistance inside the source of electrical energy - loss of PD per unit current in the source when current passes through it

ion

charged atom

ionisation

process of creating ions

isotopes

atoms of the same element with a different number of neutrons and the same number of protons

kaon

meson that has a strange quark and another quark

kinetic energy

energy of an object due to its motion

laser

produces coherent, parallel beam of monochromatic light

lepton

particles that cannot interact through the strong interation

light-dependent resistor

resistance decreases in light

limit of proportionality

limit beyond which - if a wire or spring is stretched - the extension is no longer proportional to the force applied

longitudinal waves

waves with particles that oscillate parallel to the direction of propagation of the wave

mass

measure of inertia of the motion of an object

matter waves

wave-like behaviour of particles

meson

hadron w/ quark and antiquark pair

modal dispersion

lengthening of a light pulse as it travels along optical fibre due to continual total internal reflection of waves meaning some rays travel longer distance than others in fibre

moment

about a point is the force x perpendicular distance from the line of action of the force to the point

muon

negatively charged lepton with a greater rest mass than the electron

negative temperature coefficient

resistance of a semiconductor decreases when its temperature is increased

neutrino

uncharged lepton with a lower rest mass than the electron

Newton's 1st Law of Motion

object remains at rest or in uniform motion unless acted upon by a resultant force

Newton's 2nd Law of Motion

rate of change of momentum of an object is proportional to the resultant force applied to it

node

fixed point on a stationary wave where displacement is zero

nucleon

N or P in nucleus

nucleon number

number of P's or N's in the nucleus

nuclide

type of nucleus with a particular number of P's and N's

Ohm's Law

PD across a metallic conductor is proportional to the current - if physical conditions remain constant

optical fibre

thin, flexible transparent fibre used to carry light pulses from one end to another

pair production

gamma photon changed in a particle and corresponding antiparticle

path difference

difference in the distances from two coherent sources to an interference fringe

period

time for one complete cycle of a wave to pass a point

phase difference

the fraction of a cycle between the oscillations of 2 oscillating particles - measured in radians

photoelectric effect

emission of electrons from metal surface when surface is hit with light with photons of frequency greater than threshold frequency

photon

packet or 'quantum' of electromagnetic waves