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Physics AQA AS Level > Particles and Radiation Part 1 > Flashcards

Particles and Radiation Part 1 Flashcards

1
Q

How can atoms be seen?

A

Atoms are so small that they can only be seen using an electron microscope.

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2
Q

Describe the nuclear model of the atom first proposed by Rutherford?

A
  • Small, dense, positively charged nucleus at the centre of atom composed of protons and neutrons (nucleons)
  • Negatively charged electrons orbit the nucleus at specific distances (in electron shells)
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3
Q

Conclusions proposed by the Ernest Rutherford, from the alpha-particle scattering experiment?

A
  • Positive charge is concentred at the centre of the atom
  • Mass is concentrated at the centre of the atom = very dense
  • Majority of the atom is empty space
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4
Q

What are protons and neutrons also called?

A

Nucleons

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5
Q

Relative charge of protons, neutrons + electrons?

A

Relative charge of:
Neutrons: 0
Protons: +1
Electrons: -1

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6
Q

Relative mass of protons, neutrons + electrons?

A

Relative mass of:
Neutrons: 1.0
Protons: 1.0
Electrons: 0.0005

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7
Q

Diameter of the nucleus compared to the diameter of the atom?

A

Diameter of the nucleus is 100,000x smaller than the diameter of the atom.

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8
Q

How many times smaller are electrons compared to neutrons and protons?

A

Electrons are x1800 smaller than protons and neutrons.

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9
Q

Why is an atom neutrally charged?

A

The atom is neutrally charged because the number of electrons are equal to the number of protons. The electron (negatively charged) has an equal and opposite charge to the proton (positively charged) and so they cancel each other out.

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10
Q

Define proton number/atomic number and the general letter used for it, in the nuclide notation

A
  • Has the symbol ‘Z’ (bottom left)

- Proton number is the number of protons in the nucleus.

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11
Q

Define nucleon number/mass number and the general letter used for it, in the nuclide notation

A
  • Has the symbol ‘A’ (top left)

- Nucleon number is the sum of the number of protons and neutrons in the nucleus.

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12
Q

What is the letter given to the chemical symbol in the nuclide notation

A
  • The letter X
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13
Q

Why is the mass of the total number of nucleons assumed as the atom’s relative mass?

A
  • This is because the electron’s mass is extremely small that its contribution to the total mass of the atom is insignificant.
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14
Q

Define nuclide.

A

This term is used when referring to a specific nucleus with a particular number of protons and neutrons - e.g. nucleus of a specific atom, ion or isotope)

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15
Q

Why is the nucleus positively charged?

A

This is because the nucelus is made up of protons and neutrons, where neutrons have no charge and protons are positively charged.

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16
Q

Define ion

A

Ions are charged atoms or molecules, which have lost or gained one or more electrons.

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17
Q

Different atoms form different chemical elements on the periodic table. How are atoms of different elements different to each other.?

A
  • Atoms of different elements have different numbers of protons and thus electrons
  • Atoms of the same element have the same number of protons.
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18
Q

What are isotopes?

A
  • Atoms of the same elements with the same number of protons but a different number of neutrons.

[If asked to compare isotopes we need to specify the number of protons, neutrons and electrons]

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19
Q

What are the properties of isotopes?

A
  • Different isotopes of the same element have the same chemical properties as the element because they have the same number and arrangement (configuration) of electrons in the outer shell - they determine its chemical properties
  • The number of neutrons does not affect the chemical properties of an atom however, in general the greater the number of neutrons compared to protons, the more unstable the nucleus.
  • Radioactivity is the only chemical property that changes
  • Physical properties however will change.
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20
Q

What does an unstable nuclei mean?

A

Unstable nuclei are nuclei which are radioactive and decay to become more stable.

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21
Q

What is specific charge?

A

The specific charge of a particle is its charge to mass ratio

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22
Q

Equation to calculate specific charge?

A

Specific charge = charge / mass

Ckg⁻¹ = C / kg

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23
Q

Which fundamental particle has the highest specific charge?

A

Electron, because it has the largest charge to mass ratio - the biggest charge divided by the smallest mass.

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24
Q

How else can we calculate specific charge?

A

To calculate the specific charge of a particle, we can measure the deflection of a particle (from its original line of motion) in a magnetic field

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25
Q

What force makes the nucleus unstable?

A

The electromagentic force of repulsion between the positively charged protons in the nucleus

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26
Q

When two positive charges come together, they experience a repulsive force, so how are protons held in the nucleus?

A
  • There must be another force, which is attractive between protons and stronger than the electromagnetic force of repulsion, to make the nucleus stable (by preventing it from disintegrating).
  • This force is called the strong nuclear force.
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27
Q

Is the SNF between two protons only?

A

The strong nuclear force has the same effect between two protons as it does between two neutrons as well as between a proton and a neutron.

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28
Q

LOOK AT THE GRAPH OF ‘Force between Nucleons against Distance between Nucleons’ - hide the labels and try to label it yourself.

Describe how the strength of the force of the graph changes with distance?

A
  • For seperations less than 0.5fm, the SNF is repulsive, in order to prevent the nucleus from being crushed to a point.
  • For seperations lager than 0.5fm, the SNF is attractive. Its strength initially increases until it reaches a maximum (at about 1fm) and then begins to decrease. After a seperation of 3fm has been reached, the SNF has negligible strength (virtually zero).
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29
Q

What is the diameter of the average nucleus?

A
  • The average nucleus has a diameter of about 1fm
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30
Q

Why are we not considering the gravitational force of attraction between nucleons?

A
  • Mass of nucleons are so small, that the gravitational force of attraction between them is negligible compared to the SNF of attraction (and repulsion)
  • The gravitational force of attraction is also negligible when compared to the EM force of repulsion between protons.
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31
Q

Why do the EMF never touch 0 (the x-axis)?

A

It has an infinite range. Even if it is extremely small it still exists.

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32
Q

Explain how the strong nuclear force prevents the nucleus from breaking apart.

A
  • For small separations (from 0.5fm to 3fm, the typical distance between adjacent nucleons in a nucleus) the strong nucleus force is strongly attractive, stronger than the electromagnetic force of repulsion between positively charged protons.
  • This stops the protons in the nucleus from breaking away from each other, preventing the the nucleus from disintegrating/breaking apart.
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33
Q

What is a stable nucleus?

A

A stable nucleus is a nucleus which does not disintegrate.

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34
Q
  • Unstable nuclei are considered as radioactive nuclei.

- What do unstable nuclei emit and why?

A
  • Unstable nuclei emit three different types of radiation in order to become stable.
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35
Q

What are the three types of radiation that radioactive nuclei emit.

A
  • Alpha radiation
  • Beta Radiation
  • Gamma Radiation
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36
Q

What is alpha radiation?

A
  • Usually occurs in unstable nuclei which have too large a nucleus
  • Alpha radiation emits an alpha particle composed of two protons and two neutrons (helium nucleus)
  • As a result the nucleon number decreases by 4 and the proton number decreases by 2 so its composition changes to produce a new element
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37
Q

What is the range of alpha radiation and how can you observe it?

A

Few cm in air - you can observe this using a cloud chamber (i.e. measuring tracks left in the chamber) or by measuring the count rate using a Geiger Muller Tube and counter with increasing distance from the alpha source.

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38
Q

What is Beta (minus) radiation?

A
  • Usually occurs in neutron-rich unstable nuclei
  • In which a neutron turns into a protons, which remains in the nucleus, and emits a high-speed/fast-moving electron as well as an antineutrino
  • As a result, the nucleon no. stays the same but the proton number increases by 1 so its composition changes to produce a new element
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39
Q

How did they come about the existence of the neutrino?

A

The existence of te neutrino was hypothesized to account for the conservation of energy in beta decay - the extra kinetic energy after beta decay implied the existence of another particle. The missing particle had to be chargless and massless in order to conserve charge and mass.

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40
Q

What is gamma radiation?

A
  • Usually occurs in unstable nuclei which are still in ‘high-energy’ state after beta or alpha emission
  • Gama radiation emits a gamma wave (EM radiation) which expels any left over energy in the nucleus, making it unstable
  • Gamma radiation is chargeless and massless, so composition does not change and the element remains the same.
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41
Q

What is the sign for beta particle, alpha particle, gamma wave?
What is the general equation for alpha, beta and gamma decay?

A

LOOK AT IT IN NOTES!!

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42
Q

Uses of radioactive isotopes?

A

1) Use to find out how old things are:
- All living things contain the same % of radioactive carbon-14 taken from the atmosphere
- Once they die, the amount of carbon-14 inside them ↓ as it decays into stable elements
- ∴ Approximate age can be found calculating the % of radioactive carbon-14 that is left in the dead organic matter (e.g. wood, bone) and then comparing that with isotopic data (amount of each isotope present).

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43
Q

How is energy transferred from the sun to earth through the vacuum of space?

A

Via electromagnetic waves (also referred to as light).

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44
Q

What speed does waves of the EM spectrum travel in a vacuum?

A
  • All EM Waves (Radio ➡ Gamma) travel at the same speed through a vacuum.
  • The speed of which they travel at is referred to as the speed of light (3x10⁸ms⁻¹)
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45
Q

What is the equation to calculate the speed of light?

A

Speed of light (through a vacuum) = frequency x wavelength

C = f x λ

ms⁻¹ = Hz x m

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46
Q

What did Max Planck suggest (about photons)?

A
  • EM waves(light) can only exist as discrete quantised packets of energy called photons
  • By discrete he means that the energy of these photons can only take certain values.
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47
Q
  • We said that a photon is a packet of energy.

- How can we calculate the value of a specific photon?

A
  • E = hf
  • Energy of Photon = Planck’s constant x frequency of photon
  • J = Js x Hz
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48
Q

What is Planck’s constant and where did the units come from?

A

Planck’s constant is 6.63 x 10⁻³⁴Js ( a constant of proportionality)

Units come from:

  • E = hf ➡ h = E/f
  • Frequency is measured in 1/s = s⁻¹ (as well as Hz)
  • Energy of a photon is measure in Joules (J)
  • h = J / s⁻¹ = Js
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49
Q

Describe the relationship between Energy of a photon and its frequency

A

The energy of a photon is directly proportional to its frequency.

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50
Q

How can we calculate the energy of the photon, without knowing the frequency?

A
  • c = fλ ➡ f = c/λ
  • E = hf = hc/λ
  • E = hc/λ
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51
Q

How does this equation show that EM waves have both wave elements and particle-like elements?

A
  • The use of wavelength shows the wave-like properties of an EM wave.
  • The specific discrete values of energy show the particle-like properties of an EM wave.
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52
Q

Describe the relationship between the energy of the photon and the wavelength

A
  • The energy of the photon is inversely proportional to the wavelength of the photon
    (Smaller wavelength = Higher energy photon)
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53
Q

What is an EM wave?

A

An EM wave is a wave which consists of an electric field and a magnetic field oscillating at right angles to each other and to the direction of energy transfer.

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54
Q

An EM wave is emitted by a charged particle when it loses energy.
This can happen when:

A
  • A fast-moving electron is stopped, slows down or changes direction
  • An electron in a shell moves to a different shell of lower energy.
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55
Q

A laser beam consists of photons of the same frequency. How canyou calculate the power of the beam?

A

power of a beam = nhf, where n is the number of photons passing a fixed point each second.

56
Q

What is the universe made up of?

A

The universe is made up of matter and antimatter.

57
Q

How are matter and antimatter particles formed?

A
  • Formed in pairs

- From large amounts of energy

58
Q

What does every particle have?

A

A corresponding antiparticle

59
Q

• What do both the particle and its corresponding antiparticle have in common?

A
  • Same rest mass (+ rest energy)
  • Same size (i.e. same diameter)
  • Same charge Magnitude
60
Q

What is the only known difference between a particle and its corresponding antiparticles

A
  • Opposite charge (sign)

- Opposite baryon number, lepton number and strangeness

61
Q

Define antiparticles

A

Particles with the same rest mass but opposite properties/quantum numbers (charge, strangeness etc.)

62
Q

What does the opposite electric charge between an antiparticle and particle mean?

A

If the particle and antiparticle are oppositely charged, there is an electromagnetic force of attraction between them.

63
Q

Name examples of particle and antiparticle pairs?

A
  • Electron-Positron
  • Proton-Antiproton
  • Neutron-Antineutron
  • Neutrino-Antineutrino
64
Q

Symbols for electron and positron

A

Electron : e-, β-, e

Positron: e+, β+, ē

65
Q

Relative charges of Electron and Positron

A

Electron: -1
Positron: +1

66
Q

Relative mass of Electron and Positron

A

Electron: 0.0005
Positron: 0.0005

67
Q

Symbols for Proton and Antiproton

A

Proton: p
Antiproton: p̄

68
Q

Relative charge of Proton and Antiproton

A

Proton: +1
Antiproton: -1

69
Q

Relative mass of Proton and Antiproton

A

Proton: 1.0
Antiproton: 1.0

70
Q

Symbols for Neutron and Antineutron

A

Neutron: n
Antineutron: . n̂ (should be a straight line over the n)

71
Q

Relative charge of Neutron and Antineutron

A

Neutron: 0
Antineutron: 0

72
Q

Relative mass of Neutron and Antineutron

A

Neutron: 1.0
Antiproton: 1.0

73
Q

Symbol for a Neutrino and Antineutrino:

A

Neutrino: v
Antineutrino: v̂ (should be straight line over the v)

74
Q

Relative charge for a Neutrino and Antineutrino?

A

Neutrino: 0
Antineutrino: 0

75
Q

Relative mass of Neutrino and Antrineutrino?

A

Neutrino: 0/Massless
Antineutrino: 0/Massless

76
Q

What is rest mass?

A

Rest mass of e.g. a particle, is the mass of the particle when it is stationary.

[The need for this definition is because mass can change with condition - Einstein had shown that the mass of a particles increases, the faster it travels.]

77
Q

What is rest energy?

A
  • Rest energy is the energy equivalent to the mass of a particle at rest (rest mass)
  • It is equal to the rest mass times the speed of light squared.
78
Q

What is the equation linking mass to energy that Einstein came up with?

A

(Rest) energy = (Rest) mass x speed of light²

E = mc²
J = kg x ms⁻¹

ᵣMass→ₓc²→ᵣEnergy
ᵣMass←÷c²←ᵣEnergy

79
Q

How to convert between Joules and MeV?

*MeV = Megaelectronvolts, another unit for energy

A

÷ 1.6 x 10⁻¹⁹
J——⇌——-eV
x1.6 x 10⁻¹⁹

÷ 1.6 x 10⁻¹³
J——-⇌——-MeV
x1.6 x 10⁻¹³

÷10⁶    e----⇌----MeV
x10⁶
80
Q

When calculating the rest mass of a particle, what units can we use?

A

Kg or MeV/c²

Example: Must be able to calculate MeV/c² from the kg of the particle.

  • What is the rest mass in MeV/c² of a proton with mass 1.67 x 10⁻²⁷kg?
  • E = mc²
  • E = 1.67 x 10⁻²⁷x (3x10⁸)²
  • E = 1.503 x 10⁻¹⁰J
  • J → MeV, so 1.503 x 10⁻¹⁰J / 1.6 x 10⁻¹³ = 939.375 MeV
  • m = E/c², so m = 939 MeV/c²

[ASK ABOUT THIS]

81
Q

What happens when particles meet their corresponding antiparticle?

A

When a particle meets its corresponding particle, they annihilate each other (annihilation - destroying each other) converting their total mass and the total kinetic energy before the collision into two photons (high-energy, high-frequency gamma rays) of equal energy, travelling in opposite directions, in order to conserve momentum.
- Predicted by Dirac

82
Q

Explain conservation of energy in annihilation?

A

The total energy of the antiparticle-particle pair before annihilation is equal to the total energy of the two photons after annihilation.

83
Q

What is the minimum energy that an antiparticle-particle pair can have (before annihilation)?

A
  • The sum of the rest energies of the two particles involved/particle-antiparticle pair.
  • The rest energy of one particle is represented by E₀ and because it’s a pair, that would be 2E₀.
84
Q

What is the excess energy in the photons, produced in annihilation, due to?

A

It is due to the kinetic energy of the antiparticle-particle pair.

*greater than the rest energies of the particle-antiparticle pair

85
Q

Why is momentum conserved in annihilation?

A

Momentum is conserved because the particle-antiparticle before anhilation travel towards each other in opposite direction and the two photons produced, also travel away from each other in opposite directions.

86
Q
  • Knowing that energy must be conserved, what can we say about the minimum energy that the two photons produced can have (after annihilation)?
A
  • The minimum energy of the two photons produced is equal to the sum of rest energies of the particle-antiparticle pair that annihilated each other.
  • The minimum energy that each photon has is represented by Eᴾᴴᴼᵀᴼᴺ, and because two photons are produced, that would be 2Eᴾᴴᴼᵀᴼᴺ
87
Q

Write an equation to calculate the minimum energy of a single photon in annihilation.

A
  • 2Eᴾᴴᴼᵀᴼᴺ= 2E₀ ← For 2 Photons

- Eᴾᴴᴼᵀᴼᴺ = E₀ ← For 1 Photon

88
Q

Because the energy of photon is very high…

A

…it corresponds to the gamma range (high energy) in the electromagnetic spectrum.

89
Q

What is the equation to calculate the minimum frequency of a photon, produced in annihilation of a given particl-antiparticle pair?

A
  • Eᴾᴴᴼᵀᴼᴺ = E₀
  • E = hf → Eᴹᴵᴺ = hfᴹᴵᴺ
  • Eᴾᴴᴼᵀᴼᴺ = hf → Min Eᴾᴴᴼᵀᴼᴺ = hfᴹᴵᴺ

Remember in E = hf, E always has to be in Joules!!

90
Q

Example:

Find the minimum frequency of each photon produced when a proton and antiproton annihilate.

A
  • MeV → J, so 938.28MeV x (1.6 x 10⁻¹³) = 1.50 x 10⁻¹⁰J / 6.63 x 10⁻³⁴
  • 1.50 x 10⁻¹⁰J / 6.63 x 10⁻³⁴= 2.30 x 10²³ Hz
91
Q

What is and is not conserved in annihilation?

A
  • Energy is conserved because the rest energy (as well as any kinetic energy) of the antiparticle-particle pair is converted into kinetic energy of photons
  • Momentum is conserved
  • Mass is not conserved, because the mass of the particles is changed into photons which are massless.
92
Q

What is pair production?

A
  • Opposite process of Annihilation predicted by Dirac
  • This when a particle-antiparticle pair is created from a single photon with sufficient energy passing near a nucleus or electron.
93
Q

What is the ‘sufficient energy’ in pair production?

A
  • This refers to the fact that the minimum energy a photon can have to produce a particle-antiparticle pair, is the sum of the rest energies of the two particles in the pair.
94
Q

What is the overall energy of the particle-antiparticle in pair production equal to when its not a MINIMUM?
How can this be written as an equation?

A

The overall energy of the particle-antiparticle pair is equal to the rest energy of both particles and the kinetic energy of both particles.
Eᴾᴴᴼᵀᴼᴺ = 2E₀ + 2KE

95
Q

What is the equation to calculate the minimum energy of a photon in pair production?

A

Eᴾᴴᴼᵀᴼᴺ = 2E₀

i.e. antiparticle-pair produced has no kinetic energy

96
Q

What is the equation to calculate the minimum frequency of a photon, required to cause pair production of a given particl-antiparticle pair?

A

Eᴾᴴᴼᵀᴼᴺ = 2E₀
E = hf → Eᴹᴵᴺ = hfᴹᴵᴺ
Min Eᴾᴴᴼᵀᴼᴺ = hfᴹᴵᴺ
hfᴹᴵᴺ = 2E₀

97
Q

Why do we use minimum frequency fᴹᴵᴺ?

A

In E = hf, h is a constant, so frequency is directly proportional to energy. So fᴹᴵᴺ tells you the minimum energy of the photon.

98
Q

What is the minimum frequency of a photon required to produce a proton-antiproton pair?

A

Min Eᴾᴴᴼᵀᴼᴺ = hfᴹᴵᴺ = 2E₀

  • Rest Energy of a proton, E₀, = 938.38MeV
  • MeV → J, 938.38 x (1.6 x 10⁻¹³) = 1.5 x 10⁻¹⁰ J
  • 2 x 1.5 x 10⁻¹⁰ = 3 x 10⁻¹⁰ J
  • 3 x 10⁻¹⁰ / 6.63 x 10⁻³⁴ = 4.5248 X 10²³Hz
  • = 4.52 x 10²³Hz
99
Q

What would happen if the photon had less energy than the minimum energy required?

A

-Unable to carry out pair-production (not be able to produce a particle-antiparticle pair)

100
Q

What are fundamental forces?

A

These are forces that account for all known interactions.

101
Q

What the the 4 fundamental forces?

A
  • Gravitational force
  • Electromagnetic Forces
  • Strong Nuclear Force
  • Weak Nuclear Force
102
Q

What is the gravitational force?

A
  • Attractive force that only occurs between particle/objects which have a mass.
103
Q

What is the electromagnetic force reponsible for?

A
  • The EM force is responsible for all interactions between charged particles.
  • Also responsible for making the nucleus unstable.
104
Q

Can the EM force be repulsive?

A

The EM force can be repulsive between like-charged particles

105
Q

Out of GF and EM force, why do we only have to think about EM force when talking about particles?

A

The gravitational force of attraction is negligible when compared to the EM force of repulsion between protons, that its impact is negligible.

106
Q

Which fundamental forces ONLY act on a subatomic level?

A
  • Strong Nuclear Force

- Weak Nuclear Force

107
Q

What is SNF responsible?

A
  • The SNF is responsible for keeping the nucleus stable by overcoming the electromagnetic force of attraction between the positively charged protons in the nuclus
108
Q

What is the WNF responsible for?

A
  • Responsible for changes that occur in the nucleus such as Beta-plus and Beta-minus decay.
109
Q

Relative strength of the 4 Fundamental Forces? Highest to Lowest.

*Relative to SNF

A
  • Strong Nuclear Force (1)
  • The Electromagnetic Force (10⁻³)
  • The Weak Nuclear Force (10⁻⁶)
  • The Gravitational Force (10⁻⁴⁰)
110
Q

Range of the 4 Fundamental Forces? Highest to Lowest.

A
  • Gravitatonal and Electromagnetic Force has infinite range
  • Strong Nuclear Force (10⁻¹⁵ = 1fm)
  • Weak Nuclear Force (10⁻¹⁸)
111
Q

What are the two types of Decay that interact via the weak nuclear force?

A

B⁺ Decay

B⁻ Decay

112
Q

Equation for B⁺ Decay?

A

Proton → Neutron + Positron (B⁺ particle) + Neutrino

113
Q

Equation for B⁻ Decay?

A

Neutron → Proton + Electron (B⁻ particle) + Antineutrino

114
Q

Why can’t beta decay be due to the EM force?

A

Because the neutrons are uncharged.

115
Q

During the interactions of the fundamental forces,, what is exchanged?

A
  • During these interactions, they exchange exchange particles (also known as force carriers) which bring about a force, transferring and conserving momentum, force, charge, energy, lepton number, baryon number and strangeness (except in the weak interaction).
116
Q

What exchange particle is responsible for the SNF?

A

Pions (between hadrons)

117
Q

What exchange particle is responsible for the WNF?

A

W⁺, W⁻ bosons

118
Q

What exchange particle is responsible for the EM force?

A

(virtual) photon

119
Q

What exchange particle is responsible for the gravitational force?

A

graviton (not discovered yet)

120
Q

Exchange particles interact with particles to bring about effects of attraction or repulsion or both:
1) What kind of force is brougt about by the four fundamental forces?

A
  • The strong nuclear force exchanges pions to bring about attraction or repulsion.
  • EM force exchanges photons to bring about attraction or repulsion
  • The gravitational force exhcnages gravitons to bring about attraction.
  • The weak nuclear force exchanges W and Z bosons to bring about attraction or repulsion
121
Q

Why are exchanged particles described as ‘force carriers’?

A

They are secribed as force carriers because they are thought to carry the force from one particle to the other.

122
Q

How is the force of repulsion brought about in the electromagnetic interaction?

A
  • Involves two like-charged particles e.g. two electrons
  • The exchange particle, which in this case is a virtual photon, moves from one of the electrons causing it to move backwards
  • The virtual photon is then though to carry the repulsive EM force, to the other electron, giving it momentum, and causing it to move in the direction of the exchange particle bringing about repulsion (and conserving momentum)
123
Q

Why is the exchange particle, photon termed ‘virtual’?

A

This is because in order to observe it, we would need to stop it, and this would prevent it from interacting.

124
Q

How is the force of attraction brought about in the electromagnetic interaction?

A
  • Involves two oppositely-charged particles e.g. protons and electrons
  • To visualize this, we have to assume that the exhcange particle, which in this case is the virtual photon, takes the path of a boomerang, i.e. when the virtual photon moves from the electron, the electron is ‘pushed’ towards the proton.
  • When the proton recieves the virtual photon, it is ‘pushed’ towards the electron (in the opposite direction to conserve momentum) causing attraction.
125
Q

What are the two types of W bosons?

A

W+ Boson

W- Boson

126
Q

Compare the range of the W bosons and the virtual photon.

A

Both W+ and W- bosons have a non-zero rest mass - this means unlike the massless virtual photons which have an infinite range, W Bosons act over finite range (10⁻¹⁸)

127
Q

The WNF is responsible for both beta decays.

In both decays, what is produced?

A

A particle and antiparticle:
B- decay - Electron and antineutrino
B+ decay - Positron and neutrino.

128
Q

What kind of nuclei does B+ decay take place in?

A

B+ decay occurs in unstable proton-rich nuclei.

129
Q

Draw the feymann diagrams for both beta decay.

A

LOOK AT NOTES AND SEE IF IT CORRECT.

130
Q

What does W+ boson decay into?

A

W+ bosons decays into positron and a neutrino.

131
Q

What does W- boson deca into?

A

W- bosons decay into an electron and antineutrino.

132
Q

When will the W+ and W- boson not decay into a positron/electron and neutrino/antineutrino?

A

The W+ will not decay into a positron and an neutrino, if it interacts with an antineutrino. The W- boson will not decay into an electron and antineutrino if it interacts with a neutrino. (eventhough neutrino and antineutrinos rarely react)

133
Q

If a neutron interacts with a neutrino, what will be produced? Equation? What is the force carrier?

(This happens when….during B- decay, if the W- interacts with neutrino, instead of B- decay, a neutron-neutrino interaction takes place)

A

n + Ve → p + e-
When a neutrino interacts with a neutron, via the W- boson, it changes into a proton and emits a B- particle/electron.

(This happens when….during B- decay, if the W- interacts with neutrino, instead of B- decay, a neutron-neutrino interaction takes place) - this is why the force carrier is still W- boson.

134
Q

If a proton interacts with an antineutrino, what will be produced? Equation? What is the force carrier?

A

__
p + Ve → n + e+
When an antineutrino interact with a proton, via the W+ boson, it changes into a neutron and emits a B+ particle/positron

(This happens when….during B+ decay, if the W+ interacts with an antineutrino, instead of B+ decay, a proton-antineutrino interaction takes place) - this is why the force carrier is still W+ boson.

135
Q

What is electron capture?

A

This is a type of decay that can occur in a proton-rich nucleus. A proton turns into a neutron, as a result of interacting (through the weak interaction) with an inner-shell eletron from outside of the nucleus.
The W+ boson changes the electron into a neutrino

136
Q

How else can electron capture occur?

A

Electron capture can also occur when a proton and electron collide with each other at high speed
- If the electron has sufficient energy, the overall change could also occur as a W- boson exchange from the electron to the proton.

137
Q

Draw the Feymann Diagrams for:

  • Neutron-neutrino interaction
  • Proton-antineutrino interaction
  • Electron Capture
A

LOOK AT NOTES!!

For revision purpose, electron capture is the opposite to neutron-neutrino interaction (where the W- bosonb ecomes W+)

Physics AQA AS Level (16 decks)

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