6: Nuclear Physics

Question 1

What neucleus is the most stable?

Answer 1

Iron

Question 2

Describe nucler fission.

Answer 2

When large nuclei are unstable and randomly split into two small nuclei

Question 3

Describe nuclear fussion

Answer 3

When two small neuclei combine to create a larger neucleus

Question 4

When is energy released by neucear fision or fussion?

Answer 4

When the average binding energy per neuclon is increasing.

Question 5

Difine Activity

Answer 5

The rate of decay of the radioactive nuclei in a given isotope. It is proportional to the total number of nuclei in the sample and is measured in Becquerels.

Question 6

Define Binding energy

Answer 6

The amount of energy required to split a nucleus into all its separate constituent nucleons. It is equivalent to the mass defect.

Question 7

Define chain reaction

Answer 7

​The process of the neutrons released by a fission reaction inducing further fissile nuclei to undergo fission

Question 8

Define Coolant

Answer 8

​A substance that passes through nuclear reactors and is responsible for removing heat from the core. This heat is then used to generate energy.

Question 9

Define critical mass

Answer 9

The smallest mass of fissile material required in a fission reactor for a chain reaction to be sustained.

Question 10

Define Mass defect

Answer 10

The difference in mass between a nucleus and the sum of the masses of its constituent nucleons.

Question 11

Define Moderator

Answer 11

A material in nuclear reactors that absorbs energy from fast moving neutrons, to slow them down to speeds that can be absorbed by fissile neutrons to induce fission.

Question 12

What was the rutherford scattering experement?

Answer 12

An experiment involving firing alpha particles at a thin gold foil and observing their deflections. It showed the existence and nature of the nucleus.

Question 13

What was the progression of the atomic models?

Answer 13

1803- Dalton - Indivisble particles
1897- Thompson- Plum pudding model
1911- Rutherford - Empty space and orbiting electrons
1913- - Electrons orbit in shells
1919- - Proton and neutron discovered

Question 14

What are alpha particles (radiation) properties and uses?

Answer 14

• strongly ionising
  -slow moving
• stopped by air/ paper
• deflect in a magnetic field
  Smoke detectors (smoke durtubts current of alpha particles between two metal plates)

Question 15

What are beta particles (radiation) properties and uses?

Answer 15

-Mildly ionising
-fast moving
- stopped by a few mm of aluminium
-negatively charged
- deflected in a magnetic field
Thickness detectors, if count rate is too low thickness will be ajusted.

Question 16

What are gamma particles (radiation) properties and uses?

Answer 16

• Weakly ionising
  -travels at the speed of light
  -stopped by several cm of lead of m of concrete
  -chargeless
• unaffected by magnetic and electric fields
  Used as a steriliser

Question 17

Safe use of radiation

Answer 17

Store in a lead box away from people
Time, reduce time you are in contact with the source
Distance away from the source should be a long as possibe

Question 18

What nuclei are used for nuclear fusion?

Answer 18

Deuterium and tritium

Question 19

What proton number is needed for an isotope to emitt alpha radiation?

Answer 19

greater than 60

Question 20

Inverse Square-Law: ​

Answer 20

A law that governs the intensity of gamma radiation. It means that the intensity of radiation at any point is inversely proportional to the square of the distance from its souce

Question 21

It is essential for there to be a vacuum in the chamber because

Answer 21

• To prevent the a particles being absorbed or scattered;
• By air molecules;

Question 22

Answer 22

Question 23

Answer 23

Question 24

Answer 24