# Explain why white light splits into a spectrum of colours when it passes through a glass prism.

> AQA A-Level Physics (7408) — 3.3.2 Refraction, Diffraction and Interference · Explain · 5 marks

> When a narrow beam of white light enters a glass prism, a rainbow-like band of colours emerges from the other side.

## Mark scheme (5 marks)

1. White light is made up of different wavelengths (colours / frequencies)
2. When light enters glass it slows down (entering a denser medium)
3. Shorter wavelengths slow down more than longer wavelengths (blue slows more than red)
4. Because they slow by different amounts, the different wavelengths refract (bend) by different amounts
5. This causes the colours to spread out / separate, forming a spectrum

## Related

- [Revision notes for AQA A-Level Physics (7408)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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