25 of the Physics glossary’s terms, each with the part of the syllabus where you first meet it.
The angle of incidence equals the angle of reflection, and the incident ray, reflected ray and normal lie in the same plane.
The shortening of a moving object along its direction of motion: , where is the proper length.
The direction of an induced emf is such that the current it would produce opposes the change in flux that causes it; a consequence of the conservation of energy.
The region of a space-time diagram bounded by the 45° light lines through an event, containing all the events it can affect or be affected by.
Damping small enough that the system still oscillates, with an amplitude that decreases gradually.
A semiconductor resistor whose resistance falls as the intensity of light falling on it rises.
A semiconductor device that conducts in one direction only, once the pd exceeds a threshold, and emits light when it conducts.
The distance light travels in a vacuum in one year, ; in light-years and years, .
The largest extension (or force) up to which the force on a spring or wire is proportional to its extension.
A feature of an investigation that restricts how far its conclusion applies, such as a narrow range, a single material or an untested assumption.
The straight line through the point where a force acts, in the direction of the force.
A straight line or smooth curve drawn through plotted data to show their trend, with the points spread evenly on either side and passing through the error bars.
A straight line on an HR diagram joining stars of equal radius; since , it slopes down from top left to bottom right.
The straight line joining an observer and the body observed; only motion along it produces a Doppler shift.
The product of the mass and the velocity of a body, ; a vector measured in or N s.
Rearranging a predicted relationship into the form and plotting the matching quantities, so that the relationship gives a straight line if it holds.
A published, traceable value of a quantity, from a data book, reliable database or peer-reviewed source, used to judge the accuracy of an experimental result.
A graph of against ; a straight line shows a power law , with gradient
An axis on which equal distances represent equal factors, usually powers of ten, used for data spanning many orders of magnitude.
A wave in which the particles of the medium oscillate parallel to the direction of energy transfer.
The part of a standing wave between two adjacent nodes; it is half a wavelength long and all its points oscillate in phase.
The equations and
An orbit a few hundred to about two thousand kilometres above the Earth's surface, with a period of roughly 90 to 120 minutes.
The total power radiated by a star or other body, in watts; for a black body .