# A food manufacturer uses gamma rays to sterilise packaged food before it is sent to supermarkets. Explain why gamma radiation is suitable for this purpose, and why alpha radiation would not be suitable.

> Edexcel A-Level Physics (9PH0) — 6.1 Circular motion and momentum · Explain · 5 marks

> Packaged food can be exposed to ionising radiation after sealing to extend its shelf life and make it safe to eat. The radiation must be able to pass through the packaging and reach the food inside.

## Mark scheme (5 marks)

1. Gamma rays are highly penetrating / can pass through the packaging to reach the food inside
2. Gamma rays transfer energy to / kill bacteria inside the food / sterilise the food
3. The food is irradiated (not contaminated) so it does not become radioactive itself
4. Alpha particles are weakly penetrating / stopped by a few centimetres of air or thin packaging
5. Therefore alpha radiation would not reach the food / bacteria inside the packaging and could not sterilise it

## Key terms

- [gamma ray](https://www.gradenine.co.uk/glossary/gamma-ray)
- [sterilise](https://www.gradenine.co.uk/glossary/sterilise)

## Related

- [Revision notes for Edexcel A-Level Physics (9PH0)](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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-food-manufacturer-uses-gamma-rays-62053c3b) · Published by Druglandscape Ltd.