6.4: Nuclear and Particle Physics

Question 1

Activity

Answer 1

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 2

Alpha particles

Answer 2

A type of particle consisting of two protons and two neutrons. Alpha particles are emitted in alpha decay and are strongly ionising, but weakly penetrating.

Question 3

Alpha-scattering

Answer 3

An experiment that involved firing alpha particles at a thin gold foil and detecting their subsequent motion. It provided evidence for the currently accepted model of the atom.

Question 4

Annihilation

Answer 4

The process of a particle and its antiparticle colliding and being converted into energy. The energy is released in two photons to conserve momentum.

Question 5

Antiparticles

Answer 5

All particles have a corresponding antiparticle with the same mass but opposite charge and conservation numbers.

Question 6

Beta particles

Answer 6

An electron or positron. Beta particles are emitted during beta decay and have medium ionising and penetrating capabilities.

Question 7

Beta-minus decay

Answer 7

The process of a proton inside a nucleus turning into a neutron, and emitting a beta-minus particle (an electron) and an anti-neutrino.

Question 8

Beta-plus decay

Answer 8

The process of a neutron inside a nucleus turning into a proton, and emitting a beta-plus particle (a positron) and a neutrino.

Question 9

Binding energy

Answer 9

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

Question 10

Chain reaction

Answer 10

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

Question 11

Control rods

Answer 11

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 12

Decay constant

Answer 12

The probability of decay in a unit time

Question 13

Einstein’s mass-energy equivalence

Answer 13

Mass and energy are equivalent, with the energy equivalent of a given mass being equal to the product of the mass and the speed of light squared.

Question 14

Gamma rays

Answer 14

A type of radiation emitted in gamma decay. Gamma rays are weakly ionising but very strongly penetrating.

Question 15

Hadrons

Answer 15

A class of subatomic particles that experiences the strong nuclear interaction.

Question 16

Half-life

Answer 16

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

Question 17

Isotopes

Answer 17

A form of an element with the same number of protons but different number of neutrons.

Question 18

Leptons

Answer 18

A group of elementary subatomic particles, consisting of electrons , muons and neutrinos.

Question 19

Mass defect

Answer 19

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

Question 20

Moderator

Answer 20

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 21

Nuclear Fission

Answer 21

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

Question 22

Nuclear fusion

Answer 22

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

Question 23

Nucleon number

Answer 23

The sum of the number of protons and neutrons in a given nucleus.

Question 24

Positron

Answer 24

A positively charged particle that is the antiparticle of an electron.

Question 25

Quarks

Answer 25

Fundamental particle that interacts with other quarks via the strong force interaction. They change flavour via the weak interaction and annihilate with antiquarks to form photons via the electromagnetic interaction.

Question 26

Radioactive dating

Answer 26

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

Question 27

Random nature of decay

Answer 27

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

Question 28

Strong nuclear force

Answer 28

A force that acts between nucleons in a nucleus to keep it stable. It is attractive at distances of up to 3fm and repulsive at separations less than 0.5fm.