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PHYSICS > Nuclear and Particle Physics > Flashcards

Nuclear and Particle Physics Flashcards

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1
Q

What is nucleon number?

A

The sum of the number of protons and neutrons in the nucleus

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2
Q

What is atomic number?

A

The total number of protons in the nucleus

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3
Q

Outline Rutherford’s alpha scattering experiment

A
  • High speed alpha particles were fired at a very thin sheet of gold foil.
  • The deflections of the particles were measured and conclusions were drawn
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4
Q

What was observed in the Alpha Scattering Experiment?

A
  • Most of the alpha particles passed straight through the gold atoms
  • Some of them were deflected
  • A few of them were deflected backwards
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5
Q

What is thermionic emission?

A

Thermionic emission is the release of electrons due to heating

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6
Q

Explain why electrons are released from a heated filament?

A
  • As the filament heats up, free electrons inside the metal gain kinetic energy.
  • When the surface electrons gain sufficient energy, they are released from the surface
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7
Q

What will happen to a beam of electrons it is passed through a potential difference?

A

The beam of electrons will be accelerated since work is done by the potential difference

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8
Q

How do you calculate the energy transferred to an electron, when it is accelerated across a potential difference?

A

Energy = Charge X Potential difference
Energy = eV

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9
Q

What happens when a beam of electrons is directed into a magnetic field?

A

The electron beam will be deflected since magnetic fields apply forces on moving charges

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10
Q

What is the magnitude of the force experienced by a moving electron in a magnetic field?

A

Force = Magnetic Flux Density x Charge x velocity
F = Bev

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11
Q

if the electrons are moving perpendicular to the field lines, which direction will the magnetic force act?

A

The force will act perpendicular to both the electron and field directions

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12
Q

Describe the shape of the path of a beam electrons passing through a magnetic field

A
  • The beam will produce a circular path since the magnetic force always acts perpendicular to the electrons’ motion.
  • This means it acts as a centripetal force and produces a circular path
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13
Q

What is a cyclotron?

A

A cyclotron is a particle accelerator that uses magnetic fields to accelerate particles in circular paths.

This allows higher speeds to be reached, without the limitation of the accelerator’s length

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14
Q

Describe the basic composition of a cyclotron

A

Cyclotrons consist of two D-shaped paths which are separated by a small gap.

An alternating potential difference is applied across the gap

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15
Q

How does a cyclotron work?

A
  • An electron beam is passed into the cyclotron
  • it is deflected into a circular path by a perpendicular magnetic field
  • When the beam reaches the gap, it is accelerated by a potential difference.
  • This increases the speed of the beam, causing the radius of the path to increase
  • This process repeats every half circle
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16
Q

State the equation used to calculate the circular path of an electron beam deflected in a magnetic field

A

Radius = mv/ BQ

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17
Q

What two equations must you combine to derive the radius equation?

A
  1. Centripetal force = mv^{2} / r
  2. Magnetic Force = BQv

Centripetal force = Magnetic force

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18
Q

State the mass-energy equation

A

E = mc^{2}

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19
Q

What is 1 MeV in joules?

A

(1.6 x10^{-19}) x 10^{6} = 1.6 x 10^{-13}

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20
Q

In the quark-lepton model, what are the four main categories of particles?

A
  1. Baryons
  2. Mesons
  3. Leptons
    4.Photons
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21
Q

Describe the quark composition of a baryon

A

Baryons are made up of three quarks

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22
Q

Describe the quark composition of a meson

A

Mesons are made up of a quark and antiquark pair

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23
Q

Which category of particles are classed as fundamental particles?

A

Leptons

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24
Q

Give two examples of leptons

A
  1. Electrons
  2. Neutrinos
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25
Q

What category of particles do pions belong in?

A

Mesons

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26
Q

Give two examples of baryons

A
  1. Protons
  2. Neutrons
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27
Q

What did the symmetry of the quark-lepton model predict the existence of?

A

The top quark

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28
Q

What is an antiparticle?

A

An antiparticle is one that has the same mass but opposite charge and conservation charge numbers to its corresponding particle

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29
Q

What is the antiparticle of a proton?

A

An antiproton

30
Q

What is the antiparticle of an electron?

A

A positron

31
Q

Name four things that are always conserved in a particle interaction

A
  1. Mass/ Energy
  2. Baryon number
  3. Lepton number
  4. Charge
32
Q

Describe the conservation of lepton number.

A

The Lepton number for each specific type of lepton must be the same before and after an interaction

33
Q

What two processes can cause electrons to change energy levels?

A

Excitation and Ionization

34
Q

What are the four scenarios in which an atom may become unstable?

A
  1. The atom having too many neutrons
  2. The atom having too few neutrons
  3. The atom having too much mass
  4. The atom having too much energy
35
Q

How do unstable nuclei become more stable?

A

Unstable nuclei are radioactive so emit radiation in order to become more stable
The type of radiation they emit depends of what makes them unstable

36
Q

What are the constituents of an alpha particles?

A

Two protons and two neutrons

37
Q

What are penetration capabilities of alpha radiation?

A

Alpha particles are weakly penetrating and so are stopped by a few centimeters of air or sheet of paper

38
Q

What does beta-minus radiation consist of ?

A

High-energy electrons

39
Q

What does beta-plus radiation consist of?

A

High-energy positrons

40
Q

What are the penetration capabilities of beta- minus radiation?

A

Beta-minus radiation has medium penetrative capabilities and is stopped by a few mm of aluminum or around 1 m of air

41
Q

What are the penetration capabilities of beta-plus radiation?

A

Beta-plus radiation is almost instantaneously annihilated by electrons and so has virtually zero range

42
Q

What is gamma radiation?

A

Gamma radiation is a form of high-energy electromagnetic radiation

43
Q

What charge do gamma rays have

A

Gamma rays are a form of electromagnetic radiation and so don’t have a charge

44
Q

Which type of radiation is most ionizing?

A

Alpha radiation

45
Q

Which type of radiation is most weakly ionizing?

A

Gamma radiation

46
Q

Which type of radiation travels the fastest and at what speed?

A

Gamma radiation travels the fastest since it is a type of electromagnetic radiation and so travels at the speed of light

47
Q

Under what circumstance is alpha radiation emitted?

A

When nucleus has too much mass?

48
Q

Under what circumstance is beta-minus radiation emitted?

A

Beta-minus radiation is emitted when a nucleus has too many neutrons

49
Q

Under what circumstance is beta-plus radiation emitted?

A

Beta- plus radiation is emitted when a nucleus has too many protons

50
Q

Under what circumstances is gamma radiation emitted?

A

Gamma radiation is emitted when a nucleus has too much energy

51
Q

What are the penetrative capabilities of gamma radiation?

A

Gamma radiation is highly penetrative but is absorbed by several inches of lead or several meters of concrete

52
Q

Explain the process of beta-minus decay

A

Beta-minus decay is where a neutron in the nucleus turns into a proton, and releases an electron and an electron antineutrino

53
Q

Explain the process of beta-plus decay

A

Beta-plus decay is where a proton in the nucleus turns into a neutron, and releases a positron and an electron neutrino

54
Q

How does the mass of a nucleus compare to the sum of the individual masses of its constituents?

A

The mass of the nucleus is always less the sum of the individual masses of its constituents

55
Q

What is the name given to the difference in the mass of a nucleus and its individual constituents?

A

The mass defect

56
Q

Explain why there is a mass defect in nuclei

A

The mass defect is a result of some of the mass being converted into energy used to hold the nucleus together

57
Q

What is the name for the value of the energy required to hold a nucleus together?

A

binding energy

58
Q

How can mass defect be used to calculate the binding energy of a nucleus?

A

By substituting the mass defect into Einstein’s mass energy equation

59
Q

Why isn’t it useful to compare binding energies for different nuclei?

A

Different nuclei have different numbers of nucleons

60
Q

What is a more useful measure used to compare the binding energies of different nuclei?

A

The binding energy per nucleon

61
Q

State the equation used to calculate the binding energy per nucleon of a nucleus

A

Binding Energy per Nucleon = Binding energy/ The number of nucleons

62
Q

What is the relationship between the stability of a nucleus and its binding energy per nucleon?

A

The large the binding energy per nucleon, the more stable the nucleus will be

63
Q

What is the most stable nucleus?

A

iron

64
Q

Name two nuclear processes that can be used to generate energy

A
  1. Nuclear fission
  2. Nuclear fusion
65
Q

What are the two types of fission?

A
  1. Spontaneous fission
  2. Induced fission
66
Q

Explain the basic process of induced fission

A
  1. A large nucleus absorbs a thermal neutron
  2. This causes it to split into two smaller nuclei
  3. This releases energy and at least one neutron
67
Q

Explain the basic process of fusion

A

Two smaller nuclei join together to form a larger one, and releases energy in the process

68
Q

Why is nuclear fusion not currently a feasible method of energy production?

A
  1. Nuclear fusion requires very high temperatures in order to overcome the electrostatic force between the nuclei
  2. This makes it hard to contain and means more energy must be inputted to heat the nuclei than is generated
69
Q

Where does nuclear fusion constantly take place?

A

In stars ( the sun)

70
Q
A

PHYSICS (9 decks)

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