# Explain how a star's colour and peak emission frequency can be used to determine its surface temperature, and describe what happens to the peak emission frequency of a star as its surface temperature increases.

> WJEC A-Level Physics (Wales) — 6.3 Stellar evolution and cosmology (A-Level only) · Explain · 5 marks

> Stars behave as black bodies, emitting a continuous spectrum of electromagnetic radiation. Astronomers study the light from distant stars to learn about their properties.

## Mark scheme (5 marks)

1. A black body absorbs all radiation incident on it and is an ideal emitter of radiation
2. Hotter stars emit radiation with a higher peak frequency
3. The colour of a star indicates its surface temperature — hotter stars appear blue/white and cooler stars appear red
4. As surface temperature increases, the peak emission frequency shifts towards higher frequencies (towards the blue/ultraviolet end of the spectrum)
5. A body at a constant temperature radiates the same average power that it absorbs, maintaining a stable temperature

## Key terms

- [peak emission frequency](https://www.gradenine.co.uk/glossary/peak-emission-frequency)
- [surface temperature](https://www.gradenine.co.uk/glossary/surface-temperature)

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](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-a-star-s-colour-and-484957a3) · Published by Druglandscape Ltd.