# Astronomers use spectrometers to study the light from stars. Explain how the absorption line spectrum of a star can be used to determine the chemical composition of the star's atmosphere, and why the lines appear at specific positions in the spectrum.

> Eduqas A-Level Physics — 1.6 Using radiation to investigate stars · Explain · 5 marks

> When light from a star passes through a spectrometer, a series of dark lines is observed against a continuous background of colours.

## Mark scheme (5 marks)

1. The continuous spectrum is produced by the hot interior/surface (photosphere) of the star
2. Atoms in the star's atmosphere absorb specific wavelengths/frequencies of light
3. Each element absorbs only specific wavelengths unique to that element, producing dark lines at those positions
4. The pattern/positions of the dark lines can be matched/compared to known spectra of elements measured in a laboratory
5. The elements whose absorption patterns match the observed dark lines are identified as being present in the star's atmosphere

## Key terms

- [absorption line spectrum](https://www.gradenine.co.uk/glossary/absorption-line-spectrum)
- [chemical composition](https://www.gradenine.co.uk/glossary/chemical-composition)

## Related

- [Revision notes for Eduqas A-Level Physics](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/astronomers-use-spectrometers-to-study-the-43f3eedd) · Published by Druglandscape Ltd.