# Explain why optical telescopes are often built on top of mountains or in space, rather than at sea level in populated areas.

> AQA A-Level Physics (7408) — 3.9.1 Telescopes · Explain · 5 marks

## Mark scheme (5 marks)

1. The atmosphere absorbs or distorts light (from space)
2. At high altitude / in space there is less atmosphere (above the telescope)
3. This gives a clearer / sharper image (of astronomical objects)
4. Light pollution from towns / cities makes it harder to observe faint objects
5. Remote / high-altitude sites reduce the effect of light pollution (so fainter stars or objects can be detected)

## Key terms

- [optical telescope](https://www.gradenine.co.uk/glossary/optical-telescope)

## Related

- [Revision notes for AQA A-Level Physics (7408)](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-why-optical-telescopes-are-often-d6fc2095) · Published by Druglandscape Ltd.