# A star emits electromagnetic radiation across a wide range of wavelengths. Explain how astronomers use this radiation to determine both the chemical composition and the surface temperature of the star.

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

> Different stars produce different patterns of dark lines in their spectra, and the peak wavelength of radiation they emit varies from star to star.

## Mark scheme (5 marks)

1. Stars produce a continuous spectrum of electromagnetic radiation / white light spectrum
2. Elements in the star's atmosphere absorb specific wavelengths, producing dark lines (absorption lines) in the spectrum
3. Each element produces a unique/characteristic pattern of dark lines, so the pattern of lines identifies which elements are present
4. The peak wavelength of the continuous spectrum is used to determine surface temperature
5. Hotter stars emit peak radiation at shorter wavelengths (e.g. blue/ultraviolet) and cooler stars at longer wavelengths (e.g. red/infrared)

## Key terms

- [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 "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/a-star-emits-electromagnetic-radiation-across-ad600385) · Published by Druglandscape Ltd.