# Explain what happens to the speed, frequency, and wavelength of a wave when it undergoes refraction as it moves from a less optically dense medium into a more optically dense medium.

> Cambridge International IGCSE Physics (0625) — 3.1 General properties of waves · Explain · 4 marks

## Mark scheme (4 marks)

1. The speed of the wave decreases (when entering a more optically dense medium).
2. The frequency of the wave remains unchanged / constant.
3. The wavelength of the wave decreases.
4. The wavelength decreases because speed decreases but frequency stays constant, linked by v = fλ (or equivalent correct reasoning).

## Key terms

- [refraction](https://www.gradenine.co.uk/glossary/refraction)
- [speed](https://www.gradenine.co.uk/glossary/speed)
- [frequency](https://www.gradenine.co.uk/glossary/frequency)
- [wavelength](https://www.gradenine.co.uk/glossary/wavelength)
- [optically dense medium](https://www.gradenine.co.uk/glossary/optically-dense-medium)

## Related

- [Revision notes for Cambridge International IGCSE Physics (0625)](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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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-what-happens-to-the-speed-cc93e87f) · Published by Druglandscape Ltd.