Nuclear Physics

Question 1

What is the the cause of the mass defect?

Answer 1

The binding energy is responsible

The mass of the nucleus is always less than the mass of the num of the nucleons mass.

Question 2

What is the atomic mass unit?

Answer 2

It is 1/12th of the mass of a carbon - 12 atom.

Question 3

What is the mass defect?

Answer 3

It is the difference between the total mass of the separate masses of the nucleons and the combined mass of the nucleus.

Question 4

What is the equation for the mass - energy equivalence?

Answer 4

E = mc^2

Question 5

What is the binding energy?

Answer 5

It is the energy required to separate all the nucleons on the nucleus.

Question 6

What is the binding energy per nucleon number?

Answer 6

It is the total energy required to completely separate all the nucleons in the atom.

Question 7

What makes a nucleus more stable?

Answer 7

The higher the binding energy of the nucleus, the more stable the nucleus.

Question 8

Why does the binding energy per nucleon number decreases for more higher mass nuclei?

Answer 8

It decreases because the strong nuclear force is short range and the electrostatic repulsion is long range.

Question 9

How does the forces in the nucleus difference for lower values of Ar and higher values of Ar?

Answer 9

At low values of A:
Attractive forces between nucleus will dominate over the repulsive force.

At higher values of A:
The repulsive electrostatic force begins to dominate over the attractive forces of the nucleus.

Question 10

Describe the force holding the protons.

Answer 10

The electric force binding the protons would be repulsive.

But the residual nuclear forces hold it together.

Question 11

Explain the evidence for nuclear force.

Answer 11

The force of repulsion between the nuclei is much greater than the force of attraction.
There must be some other force to hold it together.

Question 12

Describe the evidence for the nuclear force being a short range.

Answer 12

Outside the nucleus, there is a repulsion force between the protons.

The attractive force in the nucleus must only act in the nucleus.

If it is not short range, all the nuclei would stick together.

Question 13

What is the definition of the nuclear fusion.

Answer 13

it is when 2 light nuclei combine to form a nuclei of greater mass.

Question 14

What are the condition required for nuclear fusion?

Answer 14

1. Extremely high temperature of broth nuclei -> enough kinetic energy
2. Extremely high pressure -> higher chance of collisions.

Question 15

What is the nuclear fusion?

Answer 15

The splitting of a heavy nucleus into 2 lighter nuclei of similar mass.

Question 16

What are the conditions required for nuclear fission?

Answer 16

It is initiated by the capture of 1 neutron in the nucleus which has a high neutron to proton ratio

Question 17

Describe the chain reaction of uranium and an application for it.

Answer 17

When a lot of uranium is present, the neutron released undergoes a chain reactions and this releases a lot of energy.

This was used in the atom is bomb. But with neutron absorbers, we can use this is a nuclear reactor.

Question 18

How does nuclear size differ between fission and fusion reactions?

Answer 18

Fusion: Two nuclei combine to form a larger nucleus.
Fission: A large nucleus divides to form a smaller nuclei

Question 19

How does the binding energy change in a fission and fusion reaction?

Answer 19

The binding energy per nucleon number increases.

Question 20

How does the difference between the initiation of a nuclear fission reaction and a fusion reaction?

Answer 20

Fission is initiated by very high temperatures while fusion is initiated by the nuclear bombardment.

Question 21

What gets released in fission and fusion processes?

Answer 21

Fission releases energy

Fusion releases energy and neutrons.

Question 22

Explain what it means when we say that the emission of radiation in a nuclear reaction is spontaneous.

Answer 22

There is no effect by the external environment.

There is no requirement for heat or pressure.

Question 23

Explain what it means when we say that the emission of radiation in a nuclear reaction is random.

Answer 23

1. We cannot predict which nucleus in the sample decays next.
2. Cannot tell the time at which nucleus decays.
   Each nucleus has a consistent probability of decay in a fixed period of time.

Question 24

What does Decay Law mean?

Answer 24

The rate of decay of a radioactive nuclei is directly proportional to the number of radioactive nuclei in the sample.

Question 25

Explain the relationship between the number of radioactive nuclei and the rate of decay.

Answer 25

dD/dt ~ N

The rate of decay of radioactive nuclei is proportional to the number of nuclei.

Question 26

What does the decay constant mean?

Answer 26

It is the probability per unit time of decay of nucleus.

Question 27

What is the decay constant?

Answer 27

-(delta N/N)/(delta t)

Success/ sample size

Question 28

What is the half like of a nucleus?

Answer 28

It is the time taken for the number of undecayed nuclei to decrease by half.

Question 29

What is the information that we can get from the half life of nuclei.

Answer 29

It tells us how long we have to wait before it is safe

Tells us how frequently the field rod in the nuclear reactor must be charged.

Question 30

How is the activity of a nucleus measured?

Answer 30

A GM counter measures count rate using an anode.

Question 31

What is the formula for activity?

Answer 31

A = lambda * N

Question 32

What are the transmission factors for ionizing radiation/

Answer 32

1. Distance
2. Scattering
3. Absorption.

Question 33

Describe the trend in ionizing radiation strength.

Answer 33

1. Ionizing radiation strength form a point source decreases with the square of the distance it travels.
2. The intervening medium can also absorb and scatter radiation.

Question 34

Describe the detection of nuclear radiation.

Answer 34

Both dose and counts are used: depending on the application and the radiation type.

Physical doses is measured in grays and biological doses are measured in sieverts.