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A Level Physics MASTER > Particle Physics > Flashcards

Particle Physics Flashcards

To revise particle physics

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1
Q

Describe the nuclear model of the atom

A

A positive nucleus containing protons and neutrons with electrons found in shells orbiting the nucleus

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2
Q

State the relative charge of all sub atomic particles

A

Proton +1 Neutron 0 Electron -1

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3
Q

State the relative masses of all sub atomic particles

A

Proton 1 Neutron 1 Electron almost 0 (1/1840)

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4
Q

How can you calculate the specific charge? Giving all units

A

Specific charge (C/kg) = charge (C) / mass (kg)

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5
Q

Define atomic (proton number)

A

The number of protons in a nucleus = the number of electrons for an uncharged atom

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6
Q

Define nucleon number

A

The number of nucleons (protons + neutrons)

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7
Q

Define an isotope

A

An isotope is the same element with the same number of protons but different number of neutrons

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8
Q

Why is the strong nuclear force important?

A

It keeps nucleus stable

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9
Q

When is the strong nuclear force attractive

A

between 0.5 fm up to approximately 3 fm

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10
Q

When is the strong nuclear force repulsive

A

A distances closer than 0.5 fm

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11
Q

Describe some properties of the strong nuclear force

A

Very strong - overcomes repulsion between positive protons Very short range - only acts between adjacent nucleons Acts on any nucleon (proton or neutron) and is independent of charge Can be attractive or repulsive Is repulsive if nucleons gets too close - stops nuclei collapsing

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12
Q

How does the strong nuclear force cause particles to be in equilibrium?

A

Increase in nucleon separation leads to an attractive force Decrease in nucleon separation leads to a repulsive force In both situations, force will return nucleons back to equilibrium position.

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13
Q

What are the three types of radioactive decay?

A

Alpha, Beta and Gamma

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14
Q

Describe an alpha particle

A

2 protons and 2 neutrons Helium nucleus Relative mass of 4 Relative charge of +2 highly ionising Stopped by skin, paper, 5 - 10 cm of air

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15
Q

Describe a beta particle

A

fast moving electron ejected from the nucleus Relative mass of almost 0 Relative charge of -1 moderately ionising Stopped by mm’s aluminium or 1 meter of air

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16
Q

Describe a gamma wave

A

Electromagnetic wave that moves at the speed of light through a vacuum Relative mass of 0 Relative charge of 0 very weakly ionising Reduced by cm’s lead or m’s of concrete

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17
Q

Describe the evidence that neutrinos exist

A

Experimental data shows that as a beta particle is emitted in beta decay it will have a range of energies from nearly zero up to a maximum All decays must have the same energy (conservation of energy) The total energy and momentum of the beta particle and recoiling nucleus was not constant Energy has to be conserved Wolfgang pauli (1930) predicted a particle that could carry away the extra energy/momentum so they would be conserved. This particle was discovered and named the antineutrino

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18
Q

Describe the changes that take place in beta decay

A

A neutron decays into a proton creating the beta particle and an electron antineutrino For a neutron to decay into a proton a down quark decays into a up quark

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19
Q

Describe the changes that take place in positron emission

A

A proton decays into a neutron creating the positron and an electron neutrino For a proton to decay into a neutron a up quark decays into a down quark.

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20
Q

Define a fundamental particle

A

Fundamental particles cannot be divided into other particles. They have no internal structure.

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21
Q

Give some examples of fundamental particles

A

Electron, neutrino, all quarks

22
Q

What are the 6 types of quark

A

Up, down, top, bottom, strange, charm

23
Q

What is the quark structure of a proton?

A

u u d

24
Q

What is the quark structure of a neutron?

A

u d d

25
Q

What is an antiparticle

A

particles with the same mass but opposite charge

26
Q

State the name of the anti electron

A

Positron

27
Q

Define a hadron

A

Hadrons are any particle made up of quarks Hadrons are not fundamental Hadrons can be either Baryons or mesons Hadrons are subject to the strong nuclear force

28
Q

Define a baryon

A

Baryons are made up of three quarks Common baryons are protons and neutrons have a baryon number of 1

29
Q

Which is the most stable baryon?

A

Proton

30
Q

Define a meson

A

Mesons are classified as hadrons as they are made of quarks Mesons contain a quark and an antiquark have a baryon number of 0

31
Q

Name some typical mesons

A

Pi mesons and Kaons

32
Q

Name some leptons

A

Electrons, neutrinos, Tau, muon

33
Q

What force controls leptons?

A

Leptons are subject to the weak nuclear force

34
Q

What force controls hadrons?

A

hadrons are subject to the strong force

35
Q

In a nuclear event what must be conserved?

A

Charge Baryon number Lepton number

36
Q

What force of nature creates strange particles?

A

Strange particles are made through the strong interaction

37
Q

What force allows strange particles to decay?

A

Strange particles decay through the weak interaction (e.g. Kaons)

38
Q

Why must strange particles be created in pairs?

A

To conserve strangness

39
Q

When must strangeness be conserved?

A

When strange particles are made in pairs. Strangeness is conserved with the strong interaction (only the weak interaction can change the type of quark, so there must be the same number of strange particles before and after)

40
Q

When can strangeness change?

A

Strangeness can change by +1, 0 or -1 in the weak interaction when strange particles decay

41
Q

Define annihilation

A

If a particle and anti-particle meet they will annihilate each other and their entire mass is converted into energy into the form of two identical gamma photons to conserve momentum (e.g PET scanners)

42
Q

Define pair production

A

Photon interacts with a nucleus (1) • The energy of the photon is used to create a particle-antiparticle pair. (1) • To conserve momentum, the photon interacts with interacting particle. (1)

43
Q

What is the condition required for pair production?

A

This can only happen if the energy of the photon is enough to produce the mass of the particle and anti particle. This normally happens near a nucleus to conserve momentum.

44
Q

What is quark confinement?

A

The energy required to produce a separation of two quarks far exceeds the pair production energy of a quark-antiquark pair, so instead of pulling out an isolated quark, you produce mesons as the produced quark-antiquark pairs combine.

45
Q

Define an exchange particle

A

Exchange particles are how forces act between two particles They are virtual particles and only exist for a very short amount of time They can transfer energy, charge force and momentum

46
Q

For the strong nuclear force state: the particles affected and the name of the exchange particle and its range

A

Nucleons (all hadrons)

Gluons and Pions

Range up tp 3 fm

47
Q

For the electromagnetic force state: the particles affected the name of the exchange particle Range

A

Charged particles Virtual photons infinite

48
Q

For the weak nuclear force state: the particles affected the name of the exchange particle and range

A

Can effect quarks and leptons. Responsible for beta decay and changing quarks e.g u to d. W+, W- bosons 10-18 m

49
Q

For the gravitational force state: the particles affected the name of the exchange particle Range

A

all particles with mass Gravitron Infinite

50
Q

What are the rules for drawing particle interaction diagrams

A

Rules for drawing particle interaction diagrams: Exchange particles are represented by wiggly lines Other particles are represented by straight lines Incoming particles start at the bottom of the diagram and move upwards Baryons stay on one side of the diagram and leptons on the other The W boson carries charge from one side to the other (make sure charges balance) A W- particle going to the left has the same effect as a W+ moving to the right

51
Q

Why does an antineutrino need to be released during beta decay

A

To conserve, energy, momentum and lepton number

52
Q
A

A Level Physics MASTER (17 decks)

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