Nuclear Physics

Question 1

What is beta decay?

Answer 1

The emissions of a beta particle when a proton turns into a neutron in an unstable nucleus. Beta- radiation is weakly ionising. Beta+ radiation is immediately annihilated by electrons.

Question 2

What are control rods?

Answer 2

Rods found in nuclear reactors to absorb neutrons and control the rate of reaction. They can be raised or lowered depending on the rate required.

Question 3

What is the Rutherford scattering experiment?

Answer 3

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 4

What is binding energy?

Answer 4

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

Question 5

What is fission?

Answer 5

The splitting of a nucleus, to form to smaller daughter nuclei, neutrons and energy.

Question 6

What is contamination?

Answer 6

The introduction of radioactive material to another object. The object is consequently radioactive.

Question 7

What is background radiation?

Answer 7

Radiation that is found in small quantities. It originates from natural sources such as rocks and cosmic rays and man-made sources such as nuclear accidents and medical sources.

Question 8

What is half life?

Answer 8

The average time it takes for the number of radioactive nuclei in a sample to halve.

Question 9

What is fusion?

Answer 9

The joining of two smaller daughter nuclei to form a larger nucleus and release energy.

Question 10

What is alpha decay?

Answer 10

The emission of an alpha particle (2 protons, 2 neutrons) from an unstable nucleus to make it more stable. Alpha radiation is strongly ionising and is stopped by a few cm of air or a sheet of paper.

Question 11

What is radioactive dating?

Answer 11

The use of radioactive isotopes with known half lives to date objects. The isotope that is usually used is carbon-14.

Question 12

What is a moderator?

Answer 12

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

Question 13

What is mass defect?

Answer 13

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

Question 14

What is a chain reaction?

Answer 14

The process of the neutrons released by a fission reaction inducing further fissile nuclei it undergo fission.

Question 15

What is critical mass?

Answer 15

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

Question 16

What is the closest approach?

Answer 16

A method of estimating a nuclear radius by firing an alpha particle at it. It involves calculating the distance at which all the alpha particles kinetic energy is converted to electric potential energy.

Question 17

What is electron capture?

Answer 17

A process that occurs in a proton-heavy nuclei, in which an electron is drawn to the nucleus, causing a proton to transition into a neutron. An electron neutrino is also produced.

Question 18

What is activity?

Answer 18

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 19

What is inverse square law?

Answer 19

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 source.

Question 20

What is radioactive waste?

Answer 20

The waste produced from the products of fission reactions. Since the waste is unstable and radioactive, it must be stored and handled carefully.

Question 21

What is random nature of radioactive decay?

Answer 21

Radioactive decay is random, you cannot predict when a nucleus will decay or which nucleus will decay next.

Question 22

What is a coolant?

Answer 22

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 23

What is gamma decay?

Answer 23

The emission of gamma rays from an unstable nucleus that has too much energy. Gamma radiation is only very weakly ionising but requires a few cms of lead to be stopped.

Question 24

What is atomic mass unit?

Answer 24

A unit used to express atomic masses. One AMU is equal to one twelfth of the mass of a carbon atom.

Question 25

What is irradiation?

Answer 25

The exposure if an object to radiation. The exposed object does not become radioactive.