# Explain how the wavelength and frequency of a wave are related to its speed, and describe what happens to the wavelength of a wave when it passes from a medium in which it travels slowly into a medium in which it travels faster, given that the frequency remains constant.

> IB DP Physics Standard Level (2023 syllabus) — C.2 Wave model · Explain · 4 marks

## Mark scheme (4 marks)

1. Wave speed equals frequency multiplied by wavelength (v = fλ)
2. Frequency is determined by the source and does not change when the wave moves into a new medium
3. When wave speed increases and frequency is constant, wavelength must increase
4. Explicit proportional reasoning: wavelength is directly proportional to speed (at constant frequency), so wavelength increases by the same factor as the speed increases

## Key terms

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

## Related

- [Revision notes for IB DP Physics Standard Level (2023 syllabus)](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-how-the-wavelength-and-frequency-84b5b5cf) · Published by Druglandscape Ltd.