# Radioactive substances emit radiation that can be alpha, beta or gamma. Explain why gamma radiation is the most penetrating of the three types, and describe one use and one hazard of gamma radiation.

> WJEC A-Level Physics (Wales) — 6.1 Radioactivity · Explain · 5 marks

> Radioactive sources emit ionising radiation. The ability of each type of radiation to pass through materials depends on its nature and properties.

## Mark scheme (5 marks)

1. Gamma radiation has no mass (and no charge) / is electromagnetic radiation, so it interacts very little with matter
2. Gamma radiation can only be stopped / significantly absorbed by thick lead or several centimetres of concrete (whereas alpha is stopped by paper and beta by a few mm of aluminium)
3. Because gamma is weakly ionising, it loses energy slowly as it passes through materials, allowing it to travel further
4. One valid use of gamma radiation: detecting or treating cancer (radiotherapy) / sterilising medical instruments or food / medical imaging using gamma cameras
5. One valid hazard of gamma radiation: it can cause cell damage / mutations / cancer

## Key terms

- [gamma radiation](https://www.gradenine.co.uk/glossary/gamma-radiation)
- [penetrating](https://www.gradenine.co.uk/glossary/penetrating)

## 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/radioactive-substances-emit-radiation-that-can-e3b4b281) · Published by Druglandscape Ltd.