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Physics > Y1: Particles and radiation > Flashcards

Y1: Particles and radiation Flashcards

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1
Q

What is the charge of a proton

A

+1.6x10^-19 C

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2
Q

What is the charge of a neutron

A

0 C

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3
Q

What is the charge of an electron

A

-1.6x10^-19 C

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4
Q

What is the rest mass of a proton

A

1.67(3)x10^-27 kg

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5
Q

What is the rest mass of a neutron

A

1.67(5)x10^-27 kg

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6
Q

What is the rest mass of an electron

A

9.11x10^-31 kg

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7
Q

What is the Proton number (atomic number) of an atom

A

Z: The number of protons in the nucleus
- Defines the element
- In a neutral atom Z=No. of electrons

(bottom number)

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8
Q

What is the Nucleon number (mass number) of an atom

A

A: The number of protons and neutron in the nucleus
- As the mass of an electron≈0, A≈RAM of the atom

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9
Q

What is specific charge (Ckg^-1)

A

Ratio of a particle’s charge to it’s mass
(Charge/mass)

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10
Q

What are isotopes

A

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

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11
Q

How does being an isotope effect the stability of an atom

A

The greater the number of neutrons compared to the protons, the more unstable the nucleus, so it may be radioactive and decay

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12
Q

What is isotopic data

A

The relative amounts of different isotopes of an element present in a substance

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13
Q

What forces act within the nucleus of an atom

A
  • Electromagnetic force: causes the positive protons to repel each other
  • Gravitational force: Causes the nucleons to be attracted to each other due to their mass
    (EM force&raquo_space; G force)
  • Strong nuclear force: holds the nucleus together
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14
Q

How does the strong nuclear force vary with respect to distance

A
  • Repulsive for separation < 0.5fm
  • Attractive force increases past 0.5fm, up to ~3fm, after which the attraction approaches 0
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15
Q

What is nuclear decay

A

When unstable nuclei emit particles to become more stable

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16
Q

What is alpha decay

A

When an α-particle is emitted from the nucleus (2 proton and 2 neutrons, ∴ α-particle = helium atom)
- α-particle has a short range of a few cm in air
- Only occurs in very large atoms, Z>82, as the strong nuclear force can’t keep them stable)

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17
Q

What is beta-minus decay

A
  • The emission of an electron and an antineutrino
  • When a β- particle is ejected, one neutron changes into a proton (∴ occurs when isotopes are neutron rich)
  • The antineutrino particle released carries some energy and momentum to conserve the properties during the interaction
  • β- particles can travel several meters through air
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18
Q

What is a photon

A

A ‘discrete packet’ of energy all EM waves exist as (ie. light)

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19
Q

How do you calculate the energy of a photon

A

Energy of one photon (J) = Freq. (Hz) x Planck’s Constant (Js)
E = hf
∴ E = hc/λ

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20
Q

What is Planck’s constant

A

h = 6.63x10^-34 Js

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21
Q

What is an antiparticle

A

Each particle has a corresponding antiparticle with the same mass, but opposite charge

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22
Q

What is the antiparticle of a proton

A

Antiproton
- Charge = -1.6x10^-19 C
- Mass = 1.67(3)x10^-27 kg

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23
Q

What is the antiparticle for a neutron

A

Antineutron
- Charge = 0 C
- Mass = 1.67(5)x10^-27 kg

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24
Q

What is the antiparticle for an electron

A

Positron
- Charge = 1.6x10^-19 C
- Mass = 9.11x10^-31 kg

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25
Q

What is the antiparticle for a neutrino

A

Antineutrino
- Charge = 0 C
- Mass = 0 C

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26
Q

What is pair production

A

When energy is converted into mass, giving an equal amount of matter and antimatter
eg. If a photon has enough energy, it can produce an electron-positron pair (as electrons have a low mass)

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27
Q

What is the relationship between energy and the mass it can produce

A

E = mc^2

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28
Q

What is the rest energy of a particle (Eo)

A

The amount of energy that would be produced if all the mass was converted into energy

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29
Q

What is the minimum amount of energy required for pair production

A

The total rest energy of the two particles produced
∴ E(min) = 2Eo

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30
Q

What is Annihilation

A

When a particle and antiparticle meet, all of their mass is converted into energy, producing 2 gamma ray photons

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31
Q

What is the minimum energy of a photon produced during annihilation

A

The 2 photons have a total minimum energy equal to the total rest energy of the two particles
∴ E(min) = Eo

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32
Q

What are the two fundamental classes of subatomic particles

A

Bosons (Mesons and ‘photons/W-bosons/etc…’)
Fermions (Baryons and Leptons)

33
Q

What are hadrons

A

Particles made up of quarks, that feel the strong nuclear force

34
Q

What are the two types of hadrons

A
  • Baryons (3 quarks)
  • Mesons (2 quarks)
35
Q

What are baryons

A

Hadrons made up of 3 quarks (eg. nucleons)
- All will eventually decay into a proton
- Antibaryons are the antimatter of baryons, but don’t exist in ordinary matter as they are annihilated

36
Q

What is the baryon number (B)

A

A quantum number that must be conserved
- All baryons: B = +1
- All antibaryons: B = -1
- All other particles (not baryons): B = 0

37
Q

What are mesons

A

Hadrons made up of quark-antiquark pair
- All will eventually decay into pions
- Interact with baryons via the strong force
- Lots are produced in high energy particle collisions
(eg. detected in cosmic ray showers)

38
Q

What are pions (π-mesons)

A
  • The lightest mesons
  • Exchange particles for the strong nuclear force
  • Different versions with different charges
    (π+, π°, π-)
    π- = anti π+
39
Q

What are kaons (K-mesons)

A
  • Heavier and more unstable than pions
  • Have short lifetime and decay into pions
  • Different versions with different charges
    (k+, k°, k-)
    k- = anti k+
40
Q

What are Leptons

A

Fundamental particles that don’t feel the strong nuclear force, so interact via the weak interaction

41
Q

What are the different flavours of leptons

A
  • Electron (e-): Stable leptons
  • Muons (μ-): Heavier and will eventually decay into electrons

+ Tau (T): Largest lepton - Not required for AQA spec.

42
Q

What is the Lepton number

A

A quantum number that must be conserved, counted separately for different types of leptons
- Le = Electron number
- Lμ = Muon number

43
Q

What is a neutrino (V)

A
  • A neutral particle With a mass ≈ 0
  • Conserves properties during the weak interaction
  • Different flavours for different leptons (Ve, Vμ, etc.)
44
Q

What are strange particles

A

Particles that have a property called strangeness
- Created via the strong interaction
- Strangeness must be conserved, so strange particles are always created in pairs
- Decays via the weak interaction (although strangeness isn’t conserved during this)

45
Q

What properties need to be conserved during different interactions

A
  • Charge (all particle interactions)
  • Baryon number (all particle interactions)
  • Lepton number (all particle interactions, electrons/muons separately)
  • Strangeness (Only strong interaction, and some weak interactions)

(+ momentum)

46
Q

What are quarks

A

Fundamental particles that make up hadrons.
- Different flavour quarks have different properties, so determine the properties of the hadron they are contained within
- Each has a corresponding antiquark with the opposite properties

47
Q

What is the relative charge of an up quark (u)

A

+ 2/3

48
Q

What is the baryon number of an up quark (u)

A

+ 1/3

49
Q

What is the strangeness of an up quark (u)

A

0

50
Q

What is the relative charge of a down quark (d)

A

-1/3

51
Q

What is the baryon number of a down quark (d)

A

+ 1/3

52
Q

What is the strangeness of a down quark (d)

A

0

53
Q

What is the relative charge of a strange quark (s)

A

-1/3

54
Q

What is the baryon number of a strange quark (s)

A

+ 1/3

55
Q

What is the strangeness of a strange quark (s)

A

-1

56
Q

What is the quark composition of a baryon

A

Contains 3 quarks (antibaryons have 3 antiquarks), with the total of the quark properties giving the properties of the baryon

57
Q

What is the quark composition of a proton

A

uud

58
Q

What is the quark composition of a neutron

A

udd

59
Q

What is the quark composition of a meson

A

Contains 1 quark and 1 antiquark, with the total of the quark properties giving the properties of the meson

60
Q

What is the quark composition and properties of a π+ meson

A

ud̅

C = +1
S = 0

61
Q

What is the quark composition and properties of a π° meson

A

uu̅ or dd̅

C = 0
S = 0

62
Q

What is the quark composition and properties of a π̅° meson

A

uu̅ or dd̅

C = 0
S = 0

63
Q

What is the quark composition and properties of a π- meson

A

du̅

C = -1
S = 0

64
Q

What is the quark composition and properties of a k+ meson

A

us̅

C = +1
S = +1

65
Q

What is the quark composition and properties of a k° meson

A

ds̅

C = 0
S = +1

66
Q

What is the quark composition and properties of a k̅° meson

A

sd̅

C = 0
S = -1

67
Q

What is the quark composition and properties of a k- meson

A

su̅

C = -1
S = -1

68
Q

What is meant by quark confinement

A

The inability of a quark to exist by itself
- eg. If energy is directed at a proton, 1 quark won’t be removed/left alone, but the energy would turn into a quark-antiquark pair, leaving the proton as it is

69
Q

What is the weak interaction

A

A particle interaction where one quark turns into another
eg. beta +/- decay

70
Q

What is a virtual particle (gauge boson)

A

An exchange particle that only exists for a short time, allowing for a particle interaction to occur
(different types for different fundamental forces)

71
Q

What are the 4 fundamental forces, and what are their gauge bosons

A
  • Strong nuclear force: Pions (π+, π°, π-) - Affects Hadrons
  • Weak force: W bosons (+/-) - Affects all particles
  • Electromagnetic force: Virtual photons (𝛾) - Affects Charged particles

+ Gravitational force: Thought to be gravitons, but has never been directly observed - Affects all particles

72
Q

How does the size of an exchange particle effect it’s range (and therefore the range of the force)

A

The larger the mass, the shorter the range, as a large mass requires a large amount of energy to be created
- A W-boson has a mass 100x greater than a proton, so the weak interaction has a much smaller range than the strong force
- A photon has zero mass, so the EM force has an infinite range

73
Q

What is a Feynman diagram and what does it show

A

Particle interaction diagrams that show the exchange of a particle
- y-axis = time (bottom is the start)
- x-axis = displacement
- Baryons stay on the left, leptons stay on the right (if both are present)

74
Q

What happens during beta-minus decay

A

n → p + e- + V̅e
- A neutron is turned into a proton (down quark to an up quark)
- W- Boson transfers a negative charge to balance the charges

75
Q

What happens during beta-plus decay

A

p → n + e+ + Ve
- A proton is turned into a neutron (up quark to an down quark)
- W+ Boson transfers a positive charge to balance the charges

76
Q

What happens during electron capture

A

p + e- → n + Ve
- A proton ‘captures’ an electron to become a neutron
- Proton acting on an electron
∴ W+ boson is transferred from the proton to the electron, to conserve charge

77
Q

What happens during an electron-proton collision

A

p + e- → n + Ve
- A high speed electron collides with a proton, turning it into a neutron
- Electron acting on a proton
∴ W- boson is transferred from the electron to the proton, to conserve charge

78
Q

how do particles interact during electromagnetic repulsion

A
  • When particles with the same charge get close, they repel each other
  • A virtual photon is exchanged

Physics (14 decks)

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