Definitions Flashcards

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1
Q

Isotope

A

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

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2
Q

Pair Production

A

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

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3
Q

Leptons

A

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

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4
Q

Hadrons

A

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

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5
Q

Baryons

A

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

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6
Q

Mesons

A

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

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7
Q

Strangeness

A

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

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8
Q

Energy, Momentum, Charge, Baryon number and Lepton number

A

Are always conserved

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9
Q

Work Function

A

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

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10
Q

Threshold Frequency

A

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

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11
Q

Ionisation

A

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

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12
Q

Electron-volt

A

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

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13
Q

Fluorescence

A

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

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14
Q

Potential Difference

A

The work done per unit charge

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15
Q

Electro-motive force

A

The electrical energy produced per unit charge passing through the source

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16
Q

Ohm’s Law

A

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

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17
Q

Resistivity

A

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

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18
Q

Critical Temperature

A

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

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19
Q

Kirchoff’s first law

A

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

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20
Q

Kirchoff’s second law

A

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

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21
Q

Power

A

Rate at which energy is transferred

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22
Q

Internal resistance

A

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

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23
Q

Vector

A

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

24
Q

Moment

A

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

25
Q

Principle of moments

A

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

26
Q

Centre of mass

A

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

27
Q

Equilibrium

A

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

28
Q

Acceleration

A

Defined as the change in velocity per unit time

29
Q

Displacement

A

The distance in a given direction from a certain point

30
Q

Newton’s first law of motion

A

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

31
Q

Newton’s second law of motion

A

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

32
Q

Newton’s third law of motion

A

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

33
Q

Resultant force

A

The sum of all the forces acting on a body

34
Q

Principle of energy conservation

A

Energy cannot be created or destroyed

35
Q

Work done

A

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

36
Q

Efficiency

A

The useful energy out/total energy in

37
Q

Density

A

The mass per unit volume

38
Q

Hooke’s Law

A

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

39
Q

Limit of proportionality

A

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

40
Q

Elastic limit

A

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

41
Q

Tensile Stress

A

The force per unit area on a material

42
Q

Tensile Strain

A

The extension of a material divided by its original length

43
Q

Ductile

A

A material that extends with little stress

44
Q

Young’s Modulus

A

The tensile stress divided by the tensile strain

45
Q

Brittle

A

A material that undergoes very little strain

46
Q

Transverse waves

A

A wave whose oscillations are perpendicular to the direction of motion

47
Q

Longitudinal waves

A

A wave whose oscillations are parallel to the direction of motion

48
Q

Amplitude

A

The maximum displacement from equilibrium

49
Q

Wavelength

A

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

50
Q

Frequency

A

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

51
Q

Time period

A

Time taken to complete one cycle

52
Q

Principle of superposition

A

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

53
Q

Coherent

A

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

54
Q

Stationary wave

A

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

55
Q

Refraction

A

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

56
Q

Bright fringe

A

Formed when two waves overlap and reinforce

57
Q

Dark fringe

A

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