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A-Level Physics > Particles > Flashcards

Particles Flashcards

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1
Q

What is the nucleon number

A

Number of protons and neutrons and tell you atoms mass (mass number)

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2
Q

What is the equation for specific charge

A

SC = charge/mass

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3
Q

What is specific charge and what is it measured in?

A

This is the ratio of the charge of a particle to it mass and its measured in Ckg-1

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4
Q

What is an isotope?

A

Atoms with the same number of protons but different number of neutrons

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5
Q

What does changing number neutrons effect and doesn’t effect?

A
  • doesn’t effect chemical properties
  • effects nucleus’ stability ( more neutrons compared to protons = more unstable)
  • may be radioactive and decay to become more stable
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6
Q

What is isotopic data?

A

This is the relative amounts of different isotopes of an elements in a substance

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7
Q

why is most of the atom empty space?

A

Electrons orbit at large distances

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8
Q

What is mass and charge of particles measured in?

A 
Charge = coulombs 
Mass = kilograms
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9
Q

What does chemical behaviour and element reactions depend on?

A

Number of electrons in the atom

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10
Q
  • Describe alpha decay

- describe alpha particle and what to use to measure the,

A
  • happens in big atoms ( more than 82 protons) - nucleus’ are too big for the strong force
  • to make themselves stable they emit an Alpha particle from the nucleus
  • LEARN THE EQUATION
  • alpha particles have a short range (few cm in air)
  • observed using cloud chamber/ Geiger or spark counter
  • spark measures ionisation amounts
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11
Q
  • describe beta decay

- describe beta particle

A
  • it’s the emission of an electron from the nucleus along with an antineutrino
  • when nucleus ejects beta particle, a neutron from nucleus is changed to a proton
  • LEARN THE EQUATION
  • happens in neutron rich isotopes
  • antineutrino carries away some energy and momentum
  • range is several metres in air
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12
Q

Describe the hypothesis of neutrinos

A
  • 1930, Wolfgang Pauli said that another particle was emitted and carried the missing energy ( had to be neutral so charge was conserved and had to have zero or almost no mass as it would be hard to detect)
  • other discoveries led to the neutrino being accepted and detected 25 years later
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13
Q

Describe why Wolfgang Pauli thought there was another particle emitted in beta decay

A
  • originally it was thought that the only particle emitted in beta was an electron
  • observations showed energy was lost which didn’t fit conservation of energy
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14
Q

What is the electromagnetic force?

A

Causes positive protons to repel each other

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15
Q

What is the gravitational force?

A

Causes all nucleons in nucleus to attract each other due to their mass

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16
Q

What is the strong force and its range?

A
  • Works equally between all nucleons
  • at very small separations it’s repulsive (stops it crushing the nucleus)
  • to hold nucleus together must be attractive force stronger than electromagnetic
  • has very short range, only holds nucleons when separated by a few femtometers (strength falls after this)
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17
Q

Learn the diagram that shows how the strong force and electromagnetic force interact

A

Please do it

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18
Q

What is a femtometer?

A

1 fm = 1x10^-15 (size of nucleus)

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19
Q

What is annihilation?

A

This is when a particle meets its antiparticles, all mass is converted to energy, in the form of 2 gamma ray photons

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20
Q

How do you calculate minimum energy of the photon in annihilation?

A
  • Min energy of photon = rest energy of particle annihilated in MeV (Emin=Eo)
  • between particle-antiparticle which have rest energy Eo. The 2 photons have total energy of 2Eo for energy to be conserved,
  • 2Emin = 2Eo
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21
Q

What does a PET scanner do? And how do they work?

A
  • work by putting a positron emitting isotope into a bloodstream and detecting the gamma rays produced by electron-positron annihilation
  • gamma rays produced in pairs moving in opposite directions, so easy to distinguish from other gamma rays
  • radiation is detected by a scintillator
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22
Q

How did Planck and Einstein come up with photons?

A
  • Planck suggested EM waves can only be released in discrete packets or quanta
  • Einstein suggested that EM waves and their energy only exist in discrete packets (photons)
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23
Q

What is the equation for energy?

A 
E = hf 
h = Planck's constant (6.63x10^-34 Js)
f = frequency is Hz
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24
Q

How are frequency, wavelength and SOL related?

A

E = hf
f = c/wavelength
So E = hc/wavelength

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25
Q

What is frequency and what does it mean about energy?

A

Frequency is the number of complete waves passing a point per second, higher frequency means greater energy

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26
Q

What is the electromagnetic spectrum and what is it split into?

A
  • It’s a continuous spectrum of all possible frequencies of EM radiation
  • split into 7 types based on frequency and properties
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27
Q

What is wavelength?

A

The distance between two adjacent crests of a wave

28
Q

What is an antiparticle?

A
  • A particle made of antimatter
  • Each particle has one
  • they have the same mass and rest energy but different charge
29
Q

What happens when energy is converted to mass?

A

You get equal amounts of matter and antimatter

30
Q

When does pair production happen?

A
  • When there is enough energy to produce masses of the particles
  • must produce a particle and its antiparticle because quantities must be conserved
31
Q

What does the particle-antiparticle pair both have? And what does this mean?

A
  • Rest energy, Eo so min energy needed is 2Eo for there to be enough energy to produce particles (energy conserved)
  • So, Emin = 2Eo
32
Q

What is rest energy?

A

Amount of energy produced if all mass was transformed into energy

33
Q

What happens if a photon has enough energy?

A

Can produce electron-positron pair. This happens when a photon passes near the nucleus

34
Q

Why does particles produced in a detector curve away from each other in opposite directions?

A

Because they are in an applied magnetic field and have opposite charges

35
Q

Why is a electron-positron pair usually produced in pair production?

A

Because they have a low mass which means a low rest energy is needed for pair production to occur

36
Q

What can hadrons feel and leptons cant?

A

the strong nuclear force

37
Q

What are hadrons made of?

A

Quarks (they arent fundamental particles)

38
Q

What are the 2 types of hadrons?

A

Baryons and Mesons

39
Q

What is the only stable baryon?

A

Proton (all others usually decay to protons)

40
Q

Why dont you find antibaryons?

A

They are usually annihilated as soon as they are formed

41
Q

What is baryon number?

A

Number of baryons (has to be conserved)

Proton = +1, Antiproton = -1 etc

42
Q

What do mesons interact with baryons via?

A

The Strong nuclear force

43
Q

What are mesons?

A
  • They are a type of hadron that are unstable (baryon number = 0)
  • They have 2 quarks
  • found in cosmic showers
44
Q

What are the 2 types of mesons?

A

Pions and kaons

45
Q

Pions?

A
  • lightest meson
  • Can have +, - or 0
  • They are the exchange particle of the SNF
46
Q

Kaons?

A
  • Heavier and more unstable
  • can have +, - or 0
  • Shorter lifetime than pions
  • Have 2 quarks one of which is a strange quark
47
Q

how can you detect mesons?

A

Use 2 geiger counters separated by absorbing lead, if they both detect at same time = cosmic ray shower

48
Q

What do leptons react via?

A

Weak interaction (with a bit of gravitational/electromagnetic)

49
Q

What are muons?

A

heavy electrons that are unstable and decay to normal electrons

50
Q

What do electrons and muons have?

A

There own neutrinos (electron neutrino and muon neutrino) - have lepton number of +1

51
Q

What are strange particles created in?

A

Strong interaction (strangeness has to be conserved, so they’re created in pairs)

52
Q

What is the strangeness of leptons?

A

0

53
Q

What do strange particles decay via?

A

The weak interaction (strangeness not conserved in weak)

54
Q

What properties are conserved in all interactions?

A

Momentum, energy, charge, baryon number, lepton number, strangeness (except not always conserved in weak)

55
Q

When can type of quarks change?

A

in weak interaction

56
Q

Baryon quark structure?

A

qqq

57
Q

Quark confinement?

A

Can’t get a quark on its own even if energy is applied

58
Q

Quark structure of mesons?

A

Quark and an antiquark (kaons have a strange quark)

59
Q

Beta minus decay and quarks?

A

Neutron to proton ( down to up - weak interaction )

60
Q

Beta plus and quarks?

A

Proton to a neutron (up to down)

61
Q

What is an exchange particle?

A

Virtual particle which allows forces to act in a particle interaction ( determines a forces range, heavier = shorter )

62
Q

Why does the weak interaction have a short range?

A

W boson is heavier than a proton

63
Q

Exchange particle of strong interaction?

A

Pion (hadrons affected)

64
Q

Exchange particle of Electromagnetic?

A

Virtual photon (these have 0 mass so infinite range)

65
Q

Exchange particle of weak interaction?

A

W+/W- boson

66
Q

Electron capture and electron-proton collision?

A 
Same equation ( p + e- --> n + electron neutrino) but different particle acting 
Electron capture = w+
Electron proton collision = w-
67
Q

Feynman diagrams

A

Exchange particle always comes from the particle that is acting

A-Level Physics (10 decks)

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