Edexcel GCSE Physics key terms

The transfer of energy from electromagnetic radiation to an atom.

A dark line at a particular wavelength in a continuous spectrum, produced when an element absorbs that wavelength.

A pattern of dark lines produced when particular wavelengths are absorbed from a continuous spectrum.

The rate at which velocity changes, measured in metres per second squared (m/s²).

The acceleration of a freely falling object caused by gravity; near Earth's surface its magnitude is taken as 10 m/s² for this course.

The rate at which unstable nuclei decay, measured in becquerels (Bq), where 1 Bq means one decay per second.

A conductor used to transmit or receive electromagnetic waves.

The proportion of incoming radiation reflected by a surface.

A positively charged particle made of two protons and two neutrons.

Radiation consisting of helium nuclei, each containing two protons and two neutrons.

An electrical supply in which the direction of charge flow repeatedly reverses.

A voltage whose polarity repeatedly reverses, so each terminal alternates between being positive and negative relative to the other.

A generator that produces a current which repeatedly reverses direction.

An instrument connected in series to measure current in amperes (A).

The unit of electric current, with symbol A; it is also called an amp.

The maximum displacement of a point on a wave from its undisturbed or equilibrium position, measured in metres (m).

The angle between a ray approaching a boundary and the normal.

The angle between a reflected ray and the normal.

The angle between a ray travelling into a new material and the normal.

The process in which a particle and its antiparticle meet and their mass is converted into energy; in PET, a positron and electron produce two gamma-ray photons.

A human-made object placed in orbit around Earth or another body in space.

A small, mainly rocky body that orbits the Sun.

The layer of gases surrounding the Earth and held around it by gravity.

The bending and blurring of light as it passes through moving layers of air.

The pressure exerted by the air in Earth's atmosphere.

A particle containing a nucleus surrounded by electrons; it has no overall electric charge when its numbers of protons and electrons are equal.

An explanation of an atom’s structure that can be tested and changed when new evidence is found.