# Explain why a light ray changes direction when it passes from air into glass.

> Edexcel GCSE Physics (1PH0) — 4.1 Waves · Explain · 4 marks

> A ray of light travels through air and then enters a glass block. The ray changes direction at the boundary between the air and the glass.

## Mark scheme (4 marks)

1. Names the process as refraction
2. States that the speed of light decreases as it enters the glass
3. States that the wavelength decreases as the light enters the glass
4. States that the ray bends towards the normal / the angle of refraction is smaller than the angle of incidence

## Related

- [Revision notes for Edexcel GCSE Physics (1PH0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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