6.4: Nuclear and Particle Physics Flashcards
Activity
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.
Alpha particles
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.
Alpha-scattering
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.
Annihilation
The process of a particle and its antiparticle colliding and being converted into energy. The energy is released in two photons to conserve momentum.
Antiparticles
All particles have a corresponding antiparticle with the same mass but opposite charge and conservation numbers.
Beta particles
An electron or positron. Beta particles are emitted during beta decay and have medium ionising and penetrating capabilities.
Beta-minus decay
The process of a proton inside a nucleus turning into a neutron, and emitting a beta-minus particle (an electron) and an anti-neutrino.
Beta-plus decay
The process of a neutron inside a nucleus turning into a proton, and emitting a beta-plus particle (a positron) and a neutrino.
Binding energy
The amount of energy required to split a nucleus into all its separate constituent nucleons. It is equivalent to the mass defect.
Chain reaction
The process of the neutrons released by a fission reaction inducing further fissile nuclei to undergo fission.
Control rods
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.
Decay constant
The probability of decay in a unit time
Einstein’s mass-energy equivalence
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.
Gamma rays
A type of radiation emitted in gamma decay. Gamma rays are weakly ionising but very strongly penetrating.
Hadrons
A class of subatomic particles that experiences the strong nuclear interaction.
Half-life
The average time it takes for the number of radioactive nuclei in a sample of an isotope to halve.
Isotopes
A form of an element with the same number of protons but different number of neutrons.
Leptons
A group of elementary subatomic particles, consisting of electrons , muons and neutrinos.
Mass defect
The difference in mass between a nucleus and the sum of the masses of its constituent nucleons.
Moderator
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.
Nuclear Fission
The splitting a nucleus, to form two smaller daughter nuclei, neutrons and energy.
Nuclear fusion
The joining of two smaller nuclei to form a larger nucleus and to release energy.
Nucleon number
The sum of the number of protons and neutrons in a given nucleus.
Positron
A positively charged particle that is the antiparticle of an electron.
Quarks
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.
Radioactive dating
The use of radioactive isotopes with known half-lives to date objects. The isotope that is usually used is Carbon-14.
Random nature of decay
Radioactive decay is random - you cannot predict when a nucleus will decay or which nucleus will decay next.
Strong nuclear force
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.
