Wave Behaviour at Boundaries

This lesson covers the different ways waves can behave when they encounter a boundary — absorption, transmission, reflection, refraction, and diffraction — as required by the Edexcel GCSE Physics specification (1PH0), Topic 4: Waves. You also need to understand the core practical for investigating reflection and refraction of light.

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What Happens When a Wave Meets a Boundary?

When a wave meets a boundary between two different media, one or more of the following can occur:

Behaviour	Description
Absorption	The wave's energy is transferred to the material — the wave is "taken in" and its energy is converted (often to thermal energy).
Transmission	The wave passes through the material and continues on the other side.
Reflection	The wave bounces back off the boundary into the original medium.
Refraction	The wave passes through the boundary into the new medium but changes direction (due to a change in speed).

In reality, at most boundaries, a combination of these occurs. For example, when light hits glass, some is reflected, some is transmitted (and refracted), and some is absorbed.

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