# Explain what happens to the speed and wavelength of blue light and red light as they pass from air into glass, and explain why this causes white light to split into a spectrum of colours.

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

## Mark scheme (5 marks)

1. Both colours (all wavelengths of light) slow down when entering glass (a denser medium)
2. The wavelength of both colours decreases in glass
3. Blue light slows down more than red light in glass
4. Because blue light slows down more, it refracts (bends) more than red light
5. The different wavelengths therefore spread out / separate, forming a continuous spectrum (dispersion)

## Key terms

- [wavelength](https://www.gradenine.co.uk/glossary/wavelength)

## 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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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-what-happens-to-the-speed-e54e54f9) · Published by Druglandscape Ltd.