Definitions

Question 1

Isotope

Answer 1

Isotopes are atoms with the same number of protons but difference numbers of neutrons

Question 2

Pair Production

Answer 2

When a photon decays and creates a particle and its corresponding anti-particle near to a nucleus

Question 3

Leptons

Answer 3

Leptons interact through the weak nuclear force and the electromagnetic force if they are charged these are fundamental

Question 4

Hadrons

Answer 4

Hadrons interact through the strong nuclear force and the electromagnetic force if they are charged. Apart from the proton, Hadrons decay through the weak interaction

Question 5

Baryons

Answer 5

Are particles that contain 3 quarks. Protons are hadrons and all other hadrons decay into protons

Question 6

Mesons

Answer 6

Are Hadrons that contain a quark and an anti-quark and do not include protons in their decay products.

Question 7

Strangeness

Answer 7

Always conserved in a Strong interaction, particles that contain Strange or anti-strange quarks

Question 8

Energy, Momentum, Charge, Baryon number and Lepton number

Answer 8

Are always conserved

Question 9

Work Function

Answer 9

The minimum energy required by an electron to escape from a metal surface

Question 10

Threshold Frequency

Answer 10

The minimum frequency of radiation of a photon required to release an electron from a metal surface

Question 11

Ionisation

Answer 11

The energy required to remove an electron from an atom from the ground state.

Question 12

Electron-volt

Answer 12

The work done on an electron accelerating it through a potential difference of one volt.

Question 13

Fluorescence

Answer 13

Materials that absorb UV radiation and when the electrons de-excite they release photons of visible frequencies

Question 14

Potential Difference

Answer 14

The work done per unit charge

Question 15

Electro-motive force

Answer 15

The electrical energy produced per unit charge passing through the source

Question 16

Ohm’s Law

Answer 16

The potential difference across a metallic conductor is proportional to the current through it provided the physical conditions do not change

Question 17

Resistivity

Answer 17

The resistance of a material of length l and cross sectional area A

Question 18

Critical Temperature

Answer 18

A material that has zero resistivity below the critical temperature is a superconductor

Question 19

Kirchoff’s first law

Answer 19

The sum of the currents going into a junction equals the sum of the currents coming out of the junction

Question 20

Kirchoff’s second law

Answer 20

The sum of the emfs equals the sum of the pds in any closed loop

Question 21

Power

Answer 21

Rate at which energy is transferred

Question 22

Internal resistance

Answer 22

The internal resistance of a source is the loss of potential difference per unit current in the source when the current passes through the source

Question 23

Vector

Answer 23

Any physical quantity that has a direction as well as a magnitude

Question 24

Moment

Answer 24

The moment of a force about any point is defined as the force x the perpendicular distance from the line of action of the force to the point

Question 25

Principle of moments

Answer 25

The sum of the anticlockwise moments equals the sum of the clockwise moments about any pivot

Question 26

Centre of mass

Answer 26

The centre of mass of a body is the point through which a single force on the body has no turning effect

Question 27

Equilibrium

Answer 27

A body is in equilibrium when the resultant force acting on the body is zero and the sum of all the turning moments are zero

Question 28

Acceleration

Answer 28

Defined as the change in velocity per unit time

Question 29

Displacement

Answer 29

The distance in a given direction from a certain point

Question 30

Newton’s first law of motion

Answer 30

Objects either stay at rest or remain in uniform motion unless acted on by a force

Question 31

Newton’s second law of motion

Answer 31

The rate of change of linear momentum is directly proportional to the resultant force applied

Question 32

Newton’s third law of motion

Answer 32

For every force there is another force which is equal in size, opposite in direction, acts on the same line of action and is the same type of force. The two forces act on different bodies

Question 33

Resultant force

Answer 33

The sum of all the forces acting on a body

Question 34

Principle of energy conservation

Answer 34

Energy cannot be created or destroyed

Question 35

Work done

Answer 35

The energy transferred to an object equal to the product of the force and the distance moved in the direction of the force

Question 36

Efficiency

Answer 36

The useful energy out/total energy in

Question 37

Density

Answer 37

The mass per unit volume

Question 38

Hooke’s Law

Answer 38

The force needed to stretch a spring is directly proportional to the extension of the spring from its natural length

Question 39

Limit of proportionality

Answer 39

The point up to which the stress on an object is directly proportional to the strain

Question 40

Elastic limit

Answer 40

The point past which a spring will not return to its original length

Question 41

Tensile Stress

Answer 41

The force per unit area on a material

Question 42

Tensile Strain

Answer 42

The extension of a material divided by its original length

Question 43

Ductile

Answer 43

A material that extends with little stress

Question 44

Young’s Modulus

Answer 44

The tensile stress divided by the tensile strain

Question 45

Brittle

Answer 45

A material that undergoes very little strain

Question 46

Transverse waves

Answer 46

A wave whose oscillations are perpendicular to the direction of motion

Question 47

Longitudinal waves

Answer 47

A wave whose oscillations are parallel to the direction of motion

Question 48

Amplitude

Answer 48

The maximum displacement from equilibrium

Question 49

Wavelength

Answer 49

The distance between two particles with the same displacement and same velocity

Question 50

Frequency

Answer 50

The number of cycles or number of waves to pass a point per second

Question 51

Time period

Answer 51

Time taken to complete one cycle

Question 52

Principle of superposition

Answer 52

When two waves meet the total displacement at a point is equal to the vector sum of the individual displacements at that point

Question 53

Coherent

Answer 53

Two waves with the same frequency/wavelength and constant phase difference

Question 54

Stationary wave

Answer 54

Usually formed from a wave and its reflection, superposing and forming areas of maximum (Antinode) and no displacement (Node)

Question 55

Refraction

Answer 55

When a wave passes from one medium to another, changing direction and speed

Question 56

Bright fringe

Answer 56

Formed when two waves overlap and reinforce

Question 57

Dark fringe

Answer 57

Formed when two waves meet and cancel out because one wave is 180° out of phase