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Physics > 2.1 Particles > Flashcards

2.1 Particles Flashcards

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1
Q

What is a nucleon?

A

A constituent of the nucleus: a proton or a neutron

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2
Q

State a use of radioactive isotopes

A

Carbon dating - the proportion of carbon-14 in a material can be used to estimate its age

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3
Q

What is the SNF?

A

Fundamental force that keeps the nucleus stable by counteracting the electrostatic force of repulsion between protons

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4
Q

Describe the range of the SNF

A
  • repulsive up to 0.5fm
  • attractive from 0.5-3fm
    -Negligible past 3fm
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5
Q

What makes a nucleus unstable

A

Nuclei that have too many of either protons or neutrons or both

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6
Q

How do nuclei with too many nucleons decay?

A

Alpha decay

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7
Q

How do nuclei with too many neutrons decay?

A

Beta minus decay in which a neutron decays to a proton by the weak interaction ( udd to uud)

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8
Q

What is meant by beta-minus decay?

A

When a neutron turns into a proton, the atom releases an electron and an anti-neutrino

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9
Q

What occurs when an anti-particle and particle meet

A

Annihilation

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10
Q

What is the decay of americium-241 used for?

A

Smoke alarms

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11
Q

What is the decay of polonium-210 used for?

A

Ionisers

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12
Q

What force is responsible for beta decay?

A

The weak force

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13
Q

What does the weak force act on?

A

Leptons and hadrons

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14
Q

When does beta decay occur?

A

When the nucleus emits an electron or a positron

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15
Q

Why it called β- decay when a neutron decays into a proton?

A

An electron is produced

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16
Q

Why is it called β+ decay when a proton decays into a neutron?

A

A positron is produced

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17
Q

What happens to the unaccounted-for energy in beta decay?

A

It is carried away by the neutrinos

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18
Q

What happens if the nucleus is still unstable after emitting alpha or beta radiation?

A

It is in an excited state, and gives off gamma radiation

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19
Q

Why was the existence of the neutrino hypothesised?

A

To account for conservation of energy in beta decay

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20
Q

What type of particle are neutrinos?

A

Leptons

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21
Q

When are electromagnetic waves emitted?

A

When a charged particle loses energy

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22
Q

When can a charged particle lose energy (and an electromagnetic wave emitted as a result)?

A

when a fast moving electron is stopped, slows down or changes direction
when electrons move to a lower energy shell

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23
Q

In what form is electromagnetic radiation emitted?

A

Photons - bursts or packets of energy

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24
Q

What is one electron volt defined as?

A

The energy transferred when an electron is moved through a p.d. of 1V

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25
Q

What is annihilation

A

The mass of particle and antiparticle is converted back to energy, producing 2 gamma ray photons that go in opposite directions to conserve momentum

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26
Q

What is pair production

A

A gamma ray photon is converted into a particle-antiparticle pair

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27
Q

For pair production to take place the photon has to have an energy equal to or greater than
a certain minimum energy. Explain why there is a minimum energy.

A

energy of photon needs to provide at least the rest masses of both particles

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28
Q

What is the minimum energy of a photon required to make a proton-antiproton pair?

A

2 x proton rest energy
2 x 938.257 = 1876.514 MEV

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29
Q

Name the 4 fundamental forces?

A
  • Gravity
  • Electromagnetic
  • Weak nuclear force
  • Strong nuclear force
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30
Q

The virtual photon is the exchange particle of which force?

A

Electromagnetic

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31
Q

What type of particles are affected by the strong nuclear force?

A

Hadrons

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32
Q

Exchange particle of weak nuclear force

A

W boson ( W+ or W- )

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33
Q

What does the Electromagnetic force act on?

A

it acts on charged objects, for example when a positively charged ball repels another positively charged ball

34
Q

When does weak nuclear interaction occur?

A

When quark interaction changes, it affects all types of particles

35
Q

Which properties must be conversed in particle interactions? (6)

A
  • energy
  • charge
  • baryon number
  • lepton number
  • momentum
  • strangeness (only for strong interactions)
36
Q

What is a hadron?

A

composite particles that are made only of quarks (or antiquarks). The experience the strong nuclear force.

37
Q

What particles does the strong interaction affect?

A

hadrons feel the strong force only

38
Q

What is the exchange particle for strong interaction? what particles does the strong interaction affect?

A
  • gluon (for quarks)
  • pion (for nucleons)

hadrons feel the strong force only

39
Q

What is minimum energy required by the photon in pair production?

A

The rest energy of the particle pair

40
Q

Why do protons repel when they approach each other?

A

Due to the electromagnetic interaction and the exchange of a virtual photon

41
Q

Which quarks are antiprotons made up of?

A

Two antiup quarks and one antidown quark

42
Q

What is a muon?

A

A heavier relative of the electron

43
Q

How do hadrons decay?

A

Weak interaction

44
Q

What is the only stable baryon?

A

Protons

45
Q

Draw the classification of particles

A
46
Q

What is the rest energy of a particle?

A

The “energy equivalent” of the particle’s mass.

47
Q

What is an antiparticle?

A

A corresponding particle to a particle with the same mass and rest energy, but opposite charge.

48
Q

What is beta-plus decay? (2)

A
  • When a proton turns into a neutron, and a positron and neutrino are emitted.
  • It is not a natural form of decay and it only happens in experiments.
49
Q

When can pair production happen?

A

When the photon has enough energy to produce the mass of the particle and antiparticle.

50
Q

Which photons have enough energy to produce mass through pair production?

A

Gamma ray photons.

51
Q

Where does pair production usually happen and why?

A

Near the nucleus, which helps conserve momentum.

52
Q

The minimum energy of a photon in pair production is equal to…

A

…the total rest energy of the particles produced.

53
Q

What particles are affected by the weak nuclear force?

A

All types

54
Q

Compare and explain the ranges of a W boson and a photon.

A
  • W boson - Very short range because it has a large mass. This means it requires a lot of energy to create and can’t travel very far.
  • Photon - Infinite range because it has zero mass.
55
Q

What is the difference between electron capture and electron-proton collision?

A
  • In electron capture, a W+ boson travels from the proton to the electron.
  • In electron-proton collisions, a W- travels from the electron to the proton.
56
Q

What are hadrons?

A

Particles that feel the strong nuclear force. They are not fundamental.

57
Q

What are the general rules for determining the type of interaction in a reaction?

A
  • If any leptons involved at all -> Weak interaction
  • If strangeness isn’t conserved -> Weak interaction
  • All others -> Strong interaction
58
Q

What are leptons?

A

Particles that do not feel the strong interaction. They are fundamental.

59
Q

How do strange particles (e.g. kaons) interact?

A
  • Created by the strong interaction * Decay via the weak interaction
60
Q

What is unusual about strangeness?

A
  • It is not ALWAYS conserved
61
Q

What is the exchange particle for electromagnetic interaction? what particles are affected?

A
  • A virtual Photon γ. has zero rest mass + infinite range
  • only charged particles are affected
62
Q

What is the exchange particle for weak interaction? what does it affect?

A

The weak interaction exchange particle is the W boson.

The weak force affects all particle types.

63
Q

Generally, what happens when two particles interact?

A

They exert equal and opposite forces on each other

64
Q

Units for specific charge?

A

Ckg⁻¹

65
Q

What is equilibrium separation?

A

A point when the resultant force is zero and the attractive and repulsive forces balance

66
Q

what are the mesons quark compositions?

A
67
Q

What is the relative charge of protons, neutrons and electrons?

A
  • Protons = +1 * Neutrons = 0 * Electrons = -1
68
Q

What is the relative mass of protons, neutrons and electrons?

A
  • Protons = 1 * Neutrons = 1 * Electrons = 0.0005
69
Q

What is the equation for the power of a laser?

A

Power = No. of photons passing a point per second x Photon energy P = n x E = n x h x f

70
Q

Is the interaction between two distant objects instantaneous?

A

No - this is explained by the need for exchange particles, which cause forces.

71
Q

Why is an antineutrino produced in beta-minus decay, while a neutrino is produced in beta-plus decay?

A

To conserve lepton number.

72
Q

What is the difference between pions and kaons?

A

Pions - Lighter, less unstable, not strange * Kaons - Heavier, more unstable, strange

73
Q

What is quark confinement?

A

The idea that quarks cannot exist not their own.

74
Q

Describe the mass, range and charge of a W boson.

A
  • Non-zero rest mass * 0.001fm range * Can be positively or negatively charged
75
Q

Feynmann diagram for B-

A
76
Q

Feynmann diagram for B+

A
77
Q

Feynmann diagram for electronic capture

A
78
Q

Feynmann diagram for electron-proton collision

A
79
Q

Feynmann diagram for Electromagnetic repulsion

A
80
Q

range of strong nuclear force

A

10^-15

Physics (43 decks)

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