# A student shines a ray of light from water into air. The ray hits the boundary between water and air at an angle. Describe what happens to the ray of light as it crosses this boundary, and explain why this happens.

> WJEC A-Level Physics (Wales) — 2.6 Refraction of light · Describe and Explain · 5 marks

> The speed of light in water is approximately 2.25 × 10⁸ m/s, while the speed of light in air is approximately 3.00 × 10⁸ m/s.

## Mark scheme (5 marks)

1. The ray of light changes direction (refracts) as it crosses the boundary
2. The ray bends away from the normal (the angle of refraction is greater than the angle of incidence)
3. The speed of light increases as it travels from water into air
4. Refraction occurs because light travels at different speeds in different materials / media
5. The wavelength of light changes (increases) but the frequency remains the same

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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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