GCSE Physics · Edexcel 1PH0 · Topic 4B
Waves at boundaries
Key points
- When a wave meets a boundary it may be reflected, refracted (transmitted), or absorbed.
- Refraction happens because the wave changes speed in the new medium. If it enters at an angle, its direction changes.
- When a wave slows down it bends towards the normal; when it speeds up it bends away from it. Frequency stays the same; wavelength changes.
- A wave hitting the boundary along the normal changes speed but not direction.
- Sound travels faster in solids than in liquids, and faster in liquids than in gases.
- Wavefront diagrams show refraction: wavefronts get closer together where the wave is slower.
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When a wave meets a boundary between two materials, several things can happen at once. Understanding these effects explains echoes, the bending of light in water and why some materials block waves that others let through.
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