# Radio waves are used for broadcasting television and radio signals. Explain why radio waves are reflected by the ionosphere and why this property is useful for broadcasting signals across long distances on Earth.

> Pearson Edexcel International GCSE Physics (4PH1) — 3.2 The electromagnetic spectrum · Explain · 4 marks

> Radio waves are part of the electromagnetic spectrum and have the longest wavelengths and lowest frequencies of all electromagnetic waves. They travel at 3 × 10⁸ m/s in a vacuum.

## Mark scheme (4 marks)

1. Radio waves have a long wavelength (and low frequency)
2. Radio waves are reflected by the ionosphere (a layer of the atmosphere)
3. Reflection by the ionosphere sends the radio waves back down towards Earth's surface
4. This allows radio waves to travel beyond the horizon / reach receivers far away on Earth's curved surface

## Key terms

- [radio waves](https://www.gradenine.co.uk/glossary/radio-waves)
- [ionosphere](https://www.gradenine.co.uk/glossary/ionosphere)

## Related

- [Revision notes for Pearson Edexcel International GCSE Physics (4PH1)](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/radio-waves-are-used-for-broadcasting-5a200b6e) · Published by Druglandscape Ltd.