43 of the Physics glossary’s terms, each with the part of the syllabus where you first meet it.
Temperature measured from absolute zero, in kelvin: .
The uncertainty in a quantity expressed in the same units as the quantity, written as ± a value.
The lowest possible temperature, 0 K or −273 °C, at which the particles of a substance would have minimum (in the ideal gas model, zero) kinetic energy.
A continuous spectrum crossed by dark lines, produced when light passes through a cooler gas that absorbs photons whose energies match its energy-level differences.
A device that converts kinetic energy into electrical energy by rotating a coil in a magnetic field (or a magnet inside coils), producing an alternating emf.
Producing genuinely one's own work and acknowledging every idea, method, value, image or text taken from another source, including AI tools.
The rate of change of velocity, ; a vector quantity measured in .
The acceleration of a body falling under gravity alone, ; near the Earth's surface , directed downwards.
A graph of acceleration against time; the area between the line and the time axis is the change in velocity.
How close a measurement, or the mean of a set of measurements, is to the true value; it is limited by systematic errors.
The number of nuclei in a sample that decay per unit time, measured in becquerels (Bq).
A change in which no thermal energy is transferred to or from the gas (), so ; for a monatomic ideal gas
The total power scattered (reflected) by a surface or planet divided by the total power incident on it; a number from 0 to 1. The Earth's mean albedo is about 0.30.
A helium-4 nucleus (two protons and two neutrons) emitted by an unstable nucleus in alpha decay.
An emf that reverses direction periodically; a coil rotating at constant speed in a uniform field gives .
A meter that measures current, connected in series with the component; an ideal ammeter has zero resistance.
The number of particles in a sample divided by the Avogadro constant, ; measured in moles.
The maximum displacement from the equilibrium position, of an oscillating body or of the particles of a medium carrying a wave; symbol .
The angle between an incident ray and the normal at the point where the ray meets a boundary.
The rate of change of angular velocity, , measured in .
The angle through which a body has turned about an axis, measured in radians, with a sense (clockwise or anticlockwise).
times the frequency of an oscillation, , measured in
The product of a torque and the time for which it acts, , equal to the change in angular momentum; the area under a torque–time graph.
The product of moment of inertia and angular velocity, ( for a particle), measured in
The angle swept out by the radius per unit time for a body moving in a circle, , measured in ; it is related to the speed by
The meeting of a particle and its antiparticle, which disappear and are replaced by energy; an electron and a positron at rest produce two 0.511 MeV γ photons travelling in opposite directions.
A neutral particle of almost zero mass, the antiparticle of the neutrino, emitted with the electron in β⁻ decay.
A point on a standing wave where the amplitude of oscillation is a maximum, midway between two adjacent nodes.
A particle with the same mass as a given particle but the opposite charge; the positron is the antiparticle of the electron and the antineutrino that of the neutrino.
Two oscillations of the same frequency are in antiphase when their phase difference is rad (half a cycle), so one is at its positive maximum when the other is at its negative maximum.
An opening, such as a gap or slit, through which a wave passes.
The point of an orbit around the Sun that is farthest from the Sun, where the orbiting body moves slowest.
The power received per unit area from a star at the observer, ; measured in .
The force with which a support (such as bathroom scales) pushes up on a body; it differs from the true weight when the support accelerates vertically.
A unit of angle equal to 1/3600 of a degree.
A body wholly or partly submerged in a fluid experiences an upward buoyancy force equal to the weight of the fluid it displaces, .
The mean distance between the Earth and the Sun, .
The fluid resistance a satellite meets from the thin upper atmosphere; it removes energy, so the orbit shrinks and the satellite's speed increases.
The range of infrared wavelengths, about 8–13 μm, that the atmosphere absorbs only weakly, so surface radiation in this range escapes directly to space.
Light emitted high in the atmosphere near the polar regions by atoms excited by charged particles from the Sun, guided there by the Earth’s magnetic field.
The displacement of a body divided by the time taken, ; on a displacement–time graph, the gradient of the chord between two times.
The number of particles in one mole of a substance, .
The line about which a body rotates; points on it do not move as the body turns.