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Physics > Particle Physics- Unit 1 > Flashcards

Particle Physics- Unit 1 Flashcards

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1
Q

What is specific charge?

A

Total charge÷Total mass

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2
Q

Isotope definition

A

An atom with the same number of protons but a different number of neutrons

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3
Q

Specific charge units

A

Ckg^-1

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4
Q

Why must teams of scientists collaborate for advances to be made?

A

Results of experiments must be peer reviewed before they’re confirmed

Particle accelerators are expensive so collaboration helps spread the cost

Many skills and disciplines required

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5
Q

4 fundamental forces

A

Gravity
Electromagnetic
Strong nuclear
Weak nuclear

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6
Q

What does the strong nuclear force do?

A

Hold the nucleus of atoms together because gravity is too weak at this scale.
Is also responsible for decay/creation of particles

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7
Q

What does the weak nuclear force do?

A

Responsible for the decay/creation of atoms

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8
Q

What does the electromagnetic force do?

A

All objects with charge are repelled or attracted to eachother

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9
Q

What does gravity do?

A

All objects with mass are attracted to eachother

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10
Q

What is 1 femtometer in meters

A

1x10^-15

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11
Q

What happens to the SNF is nucleons are 0-0.5 fm apart

A

It is repulsive

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12
Q

What happens to the SNF if nucleons are 0.5-3 fm apart

A

It is attractive

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13
Q

What happens to the SNF beyond 3 fm?

A

No effect

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14
Q

When does beta minus decay occur?

A

When a nucleus is neutron rich(has too many neutrons)

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15
Q

When does alpha decay occur?

A

Unstable nucleus
-Too much mass
-Too much energy
-Imbalance of protons/neutrons

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16
Q

What is produced in beta minus decay?

A

Anti neutrino

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17
Q

What is the energy of a photon directly proportional to?

A

It’s frequency

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18
Q

What property is the same in a particle and it’s corresponding antiparticle?

A

Mass

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19
Q

What happens when matter and antimatter meet?

A

They annihilate

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20
Q

What energy is released in annihilation?

A

The rest energy(energy stored in the mass of the matter/antimatter)

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21
Q

How many joules in one electronvolt

A

1mev=1.6x10^-19 J

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22
Q

Mega prefix

A

10^6

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23
Q

What is pair production

A

A high energy photon converts it’s energy into a particle and corresponding antiparticle pair

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24
Q

What is needed for a photon to produce a particle and an antiparticle?

A

It’s energy at a minimum must equal the rest energies of the 2 particles produced

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25
Q

The more energetic the photon:

A

-Heavier particles produced
-Particles with extra kinetic energy
-Lots of smaller particles

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26
Q

How are the photons emitted after annihilation?

A

They are emitted in opposite directions to conserve momentum

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27
Q

What’s the difference between baryons and mesons?

A

Baryons are made of 3 quarks
Mesons are made of a quark and an antiquark

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28
Q

Hadrons vs leptons

A

-Hadrons feel the SNF, leptons can’t
-Hadrons can be broken up into quarks whereas leptons are fundamental

29
Q

What’s the only stable hadron?

A

Protons

30
Q

What’s the only stable lepton?

A

Electrons

31
Q

What’s a muon?

A

A big unstable electron

32
Q

4 meson rules to find quark composition of a meson

A

-Must contain a quark + antiquark
-Charge must add up to +1,-1,0
-If strangeness=0 - - > pion
-If strangeness≠0 - - > Kaon

33
Q

What is always conserved?

A

Charge
Baryon number
Lepton electron number
Lepton muon number
Strangeness(Strong interaction)

34
Q

Exchange particle of electromagnetic force

A

Virtual photon

35
Q

Exchange particle of weak nuclear force

A

W+ and W- bosons

36
Q

Exchange particle of strong nuclear force

A

Pions if force between nucleus
Gluons if force between quarks

37
Q

Feynman diagram rules

A

Before interaction at bottom
After interaction at top
Baryons on the left
Leptons on the right

38
Q

Range of weak nuclear force

A

Very short

39
Q

Range of strong nuclear force

A

3fm

40
Q

Range of gravity

A

Infinite

41
Q

Range of electromagnetic force

A

Infinite

42
Q

How is the nucleon number calculated.

A

Is it calculated from the different isotopes that exist for each element

43
Q

What quark transformation happens in beta minus decay

A

Down quark becomes up quark

44
Q

How does the weak nuclear force operate

A

It used w+ or W- bosons or conserve energy/momentum

45
Q

Proton quark composition

A

Uud

46
Q

Neutron quark composition

A

Udd

47
Q

Why do SNF and wnf have short ranges?

A

The mass of these large exchange particles require large amounts of energy to be borrowed (to create it). Meaning, it only exists for a short time and hence had a short range.

48
Q

Why must the strong nuclear force be repulsive at small separations?

A

If it wasn’t it would crush nucleus to a point

49
Q

Range of alpha particles

A

Short range in air

50
Q

How were neutrinos hypothesised?

A

-Experiments showed the energy of particles after Bega decay was less than before
-Wolfgang Paulo suggested another particle was emitted too which carried the missing energy
-Had to be neutral to conserve charge
-Observed 25 years later

51
Q

What is the minimum energy for pair production

A

Total rest energy of the particles produced

52
Q

Quark confinement

A

It’s not possible to get a quark by itself

53
Q

When is strangeness always conserved?
When is it sometimes conserved?

A

Always: Strong interaction
Sometimes: Weak interaction

54
Q

How do mesons interact with baryons?

A

Via the strong force

55
Q

How are strange particles created and decayed?

A

Created via strong interaction
Decayed by weak interaction

56
Q

Kaons

A

Kaons are heavier and more unstable than pions
Short lifetime
Decay into pions

57
Q

Name the particle believed to be responsible for mass

A

Higgs boson

58
Q

Name the particle that is difficult to detect

A

Anti neutrino

59
Q

Beta minus decay exchange particle

A

W- boson

60
Q

Exchange particle definition

A

Force carrier for the 4 fundamental forces

61
Q

Explain why there is a minimum energy for a photon to do pair production

A

Because the photon needs to provide enough energy to provide for the rest mass

62
Q

Explain why there is a minimum energy for pair production

A

Energy of photon just provide at least the rest masses of the particle and antiparticle

63
Q

How to calculate frequency of annihilation

A

Find the energy first
Then you need to divide this by 2
Because there are 2 photons

64
Q

Role or exchange particles

A

-Transfer energy
-Transfer momentum
-Transfer force

65
Q

Why are 2 photons produced in annihilation?

A

momentum must be conserved

so need two photons travelling in different direction

66
Q

How do we know if an interaction is WNF?

A

-Strangeness not conserved
-Decay

67
Q

electron capture and electron-proton collision equation

A

p+e- -> n + ve

68
Q

Electron capture exchange particle

A

W+ boson

69
Q

Electron proton collision exchange particle

A

W- boson

Physics (10 decks)

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