Nuclear and Particle Physics

Question 1

What is nucleon number?

Answer 1

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

Question 2

What is atomic number?

Answer 2

The total number of protons in the nucleus

Question 3

Outline Rutherford’s alpha scattering experiment

Answer 3

• 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

Question 4

What was observed in the Alpha Scattering Experiment?

Answer 4

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

Question 5

What is thermionic emission?

Answer 5

Thermionic emission is the release of electrons due to heating

Question 6

Explain why electrons are released from a heated filament?

Answer 6

• 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

Question 7

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

Answer 7

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

Question 8

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

Answer 8

Energy = Charge X Potential difference
Energy = eV

Question 9

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

Answer 9

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

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 12

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

Answer 12

• 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

Question 13

What is a cyclotron?

Answer 13

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

Question 14

Describe the basic composition of a cyclotron

Answer 14

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

An alternating potential difference is applied across the gap

Question 15

How does a cyclotron work?

Answer 15

• 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

Question 16

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

Answer 16

Radius = mv/ BQ

Question 17

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

Answer 17

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

Centripetal force = Magnetic force

Question 18

State the mass-energy equation

Answer 18

E = mc^{2}

Question 19

What is 1 MeV in joules?

Answer 19

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

Question 20

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

Answer 20

1. Baryons
2. Mesons
3. Leptons
   4.Photons

Question 21

Describe the quark composition of a baryon

Answer 21

Baryons are made up of three quarks

Question 22

Describe the quark composition of a meson

Answer 22

Mesons are made up of a quark and antiquark pair

Question 23

Which category of particles are classed as fundamental particles?

Answer 23

Leptons

Question 24

Give two examples of leptons

Answer 24

1. Electrons
2. Neutrinos

Question 25

What category of particles do pions belong in?

Answer 25

Mesons

Question 26

Give two examples of baryons

Answer 26

1. Protons 2. Neutrons

Question 27

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

Answer 27

The top quark

Question 28

What is an antiparticle?

Answer 28

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

Question 29

What is the antiparticle of a proton?

Answer 29

An antiproton

Question 30

What is the antiparticle of an electron?

Answer 30

A positron

Question 31

Name four things that are always conserved in a particle interaction

Answer 31

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

Question 32

Describe the conservation of lepton number.

Answer 32

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

Question 33

What two processes can cause electrons to change energy levels?

Answer 33

Excitation and Ionization

Question 34

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

Answer 34

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

Question 35

How do unstable nuclei become more stable?

Answer 35

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

Question 36

What are the constituents of an alpha particles?

Answer 36

Two protons and two neutrons

Question 37

What are penetration capabilities of alpha radiation?

Answer 37

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

Question 38

What does beta-minus radiation consist of ?

Answer 38

High-energy electrons

Question 39

What does beta-plus radiation consist of?

Answer 39

High-energy positrons

Question 40

What are the penetration capabilities of beta- minus radiation?

Answer 40

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

Question 41

What are the penetration capabilities of beta-plus radiation?

Answer 41

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

Question 42

What is gamma radiation?

Answer 42

Gamma radiation is a form of high-energy electromagnetic radiation

Question 43

What charge do gamma rays have

Answer 43

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

Question 44

Which type of radiation is most ionizing?

Answer 44

Alpha radiation

Question 45

Which type of radiation is most weakly ionizing?

Answer 45

Gamma radiation

Question 46

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

Answer 46

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

Question 47

Under what circumstance is alpha radiation emitted?

Answer 47

When nucleus has too much mass?

Question 48

Under what circumstance is beta-minus radiation emitted?

Answer 48

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

Question 49

Under what circumstance is beta-plus radiation emitted?

Answer 49

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

Question 50

Under what circumstances is gamma radiation emitted?

Answer 50

Gamma radiation is emitted when a nucleus has too much energy

Question 51

What are the penetrative capabilities of gamma radiation?

Answer 51

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

Question 52

Explain the process of beta-minus decay

Answer 52

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

Question 53

Explain the process of beta-plus decay

Answer 53

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

Question 54

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

Answer 54

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

Question 55

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

Answer 55

The mass defect

Question 56

Explain why there is a mass defect in nuclei

Answer 56

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

Question 57

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

Answer 57

binding energy

Question 58

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

Answer 58

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

Question 59

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

Answer 59

Different nuclei have different numbers of nucleons

Question 60

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

Answer 60

The binding energy per nucleon

Question 61

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

Answer 61

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

Question 62

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

Answer 62

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

Question 63

What is the most stable nucleus?

Answer 63

iron

Question 64

Name two nuclear processes that can be used to generate energy

Answer 64

1. Nuclear fission 2. Nuclear fusion

Question 65

What are the two types of fission?

Answer 65

1. Spontaneous fission 2. Induced fission

Question 66

Explain the basic process of induced fission

Answer 66

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

Question 67

Explain the basic process of fusion

Answer 67

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

Question 68

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

Answer 68

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

Question 69

Where does nuclear fusion constantly take place?

Answer 69

In stars ( the sun)