# Describe how astronomers use the electromagnetic radiation received from a star to determine its surface temperature and what they can conclude about a star's chemical composition.

> WJEC A-Level Physics (Wales) — 1.6 Using radiation to investigate stars · Describe · 5 marks

> Stars emit electromagnetic radiation across a range of wavelengths. By studying this radiation carefully, astronomers can discover a great deal about the physical properties of stars that are too far away to visit.

## Mark scheme (5 marks)

1. The colour / peak wavelength of the radiation emitted by a star indicates its surface temperature
2. Hotter stars appear blue/white and cooler stars appear red/orange
3. The spectrum of a star contains dark absorption lines
4. These absorption lines are caused by elements in the star's outer atmosphere absorbing specific wavelengths
5. Each element produces a unique/characteristic pattern of lines, so the chemical composition of the star can be identified

## Key terms

- [electromagnetic radiation](https://www.gradenine.co.uk/glossary/electromagnetic-radiation)
- [surface temperature](https://www.gradenine.co.uk/glossary/surface-temperature)
- [chemical composition](https://www.gradenine.co.uk/glossary/chemical-composition)

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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/describe-how-astronomers-use-the-electromagnetic-e4cc7c5f) · Published by Druglandscape Ltd.