Refraction: GCSE Physics Definition

What is refraction?

In GCSE physics, refraction describes the change in the direction of a wave when it passes from one medium to another.

When a wave arrives at the boundary between two media, it either bends towards or away from a line perpendicular to the boundary called the normal. The direction the wave bends depends on the densities of the two media. This is more easily shown using a ray diagram, where a ray is a straight line indicating the direction of the wave.

The ray that approaches the boundary is known as the incident ray. The angle between the incident ray and the normal is known as the angle of incidence, . The ray that leaves the boundary is known as the refracted ray. The angle between the refracted ray and the normal is known as the angle of refraction, .

If the wave enters a denser medium (e.g. air to glass):

• the ray refracts towards the normal

• the angle of incidence is larger than the angle of refraction,

If the wave enters a less dense medium (e.g. glass to air):

• the ray refracts away from the normal

• the angle of refraction is larger than the angle of incidence,

Refraction revision resources to ace your exams

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