# A hospital uses a radioactive source to sterilise medical equipment. The source emits alpha particles, beta particles and gamma rays. Explain why gamma rays are chosen for this purpose rather than alpha particles or beta particles, referring to the properties of each type of radiation.

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

> Radioactive sources emit ionising radiation that can be used in a variety of medical and industrial applications. The type of radiation chosen for a particular use depends on its penetrating power and its ionising ability.

## Mark scheme (5 marks)

1. Alpha particles have very low penetrating power / are stopped by a few centimetres of air or a sheet of paper
2. Alpha particles would not penetrate the medical equipment / packaging to sterilise it
3. Beta particles have moderate penetrating power / are stopped by a few millimetres of aluminium
4. Gamma rays have the greatest penetrating power / can penetrate thick materials including the equipment and packaging
5. Gamma rays can therefore reach and kill bacteria / microorganisms inside the packaging, making it suitable for sterilisation

## Key terms

- [alpha particles](https://www.gradenine.co.uk/glossary/alpha-particles)
- [beta particles](https://www.gradenine.co.uk/glossary/beta-particles)
- [gamma rays](https://www.gradenine.co.uk/glossary/gamma-rays)
- [sterilise](https://www.gradenine.co.uk/glossary/sterilise)

## 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/a-hospital-uses-a-radioactive-source-d1252e92) · Published by Druglandscape Ltd.