# A star appears white when viewed from Earth. Over millions of years, the star cools and its colour changes to red. Explain, in terms of the electromagnetic spectrum, why the colour of the star changes as it cools.

> Eduqas GCSE Physics — 2.1 Light, lenses and the universe · Explain · 4 marks

> Stars emit light across a range of wavelengths. The peak wavelength of light emitted by a star depends on its surface temperature.

## Mark scheme (4 marks)

1. Hotter objects emit radiation at shorter (peak) wavelengths / cooler objects emit radiation at longer (peak) wavelengths
2. Red light has a longer wavelength than white/blue-white light in the visible spectrum
3. As the star cools, the peak wavelength of emitted radiation shifts towards / into the red region of the visible spectrum
4. Therefore the star appears red because the dominant/peak wavelength detected corresponds to red light

## Key terms

- [electromagnetic spectrum](https://www.gradenine.co.uk/glossary/electromagnetic-spectrum)

## Related

- [Revision notes for Eduqas GCSE Physics](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-appears-white-when-viewed-6c0ce877) · Published by Druglandscape Ltd.