Edexcel GCSE Physics key terms

A measure of the effect of radiation received by a person, expressed in sieverts (Sv).

Describes an unstable nucleus that spontaneously emits radiation as it decays.

The unwanted presence of radioactive material on or inside an object or organism.

The spontaneous, random change of an unstable nucleus accompanied by the emission of radiation.

A radioactive substance whose emissions can be detected to follow where the substance travels or collects.

Material containing unstable nuclei that emit ionising radiation and therefore requires controlled handling, storage and disposal.

An isotope with an unstable nucleus that undergoes radioactive decay.

A radioactive atom attached to a carrier molecule selected for a particular medical purpose.

Treatment that uses ionising radiation to damage and kill cancer cells.

A radioactive isotope incorporated into a substance so that its movement or distribution can be detected.

An electromagnetic wave in the lowest-frequency, longest-wavelength region of the electromagnetic spectrum.

Electromagnetic radiation used to carry signals for broadcasting and other wireless communications.

A naturally occurring radioactive gas produced as uranium in rocks and soil decays.

Motion with continually changing, unpredictable directions because particles undergo collisions.

A process in which the exact outcome of an individual event cannot be predicted, although probabilities and overall patterns can be described.

A region in a longitudinal wave where particles are further apart and the pressure or density is lower.

How much a quantity changes per unit time.

Change in a quantity divided by the time taken for that change.

The decrease in an object's temperature per unit time.

The time between the driver recognising a hazard and applying the brakes.

The central region of a nuclear reactor containing the fuel and the components used to control the chain reaction.

An image formed where light rays from an object actually meet. It can be projected onto a screen placed at the image position.

Movement away from an observer, so that the distance between the source and observer increases.

A late stage of a Sun-like star in which its outer layers expand and cool, making the star much larger and redder.

An increase in the observed wavelength of light, with its spectral lines displaced towards the red end of the visible spectrum.

A very large star with expanded, cooler outer layers, formed late in the life of a massive star.

The change in direction of a wave when it bounces off a surface.

The change in direction of a wave at a boundary between substances when its speed changes.