# Explain why alpha radiation is more ionising than gamma radiation.

> OCR GCSE Physics A: Gateway Science (J249) — P4.3 Radioactive emissions · Explain · 4 marks

> Scientists studying radioactive sources measure how effectively different types of radiation can ionise the air around them. They find that alpha particles cause far more ionisation per centimetre of path than gamma rays do.

## Mark scheme (4 marks)

1. Alpha particles are relatively large / have a large mass (compared to gamma)
2. Alpha particles carry a charge (of +2) / interact strongly with electrons in atoms
3. Alpha particles transfer energy to / knock electrons from atoms more readily, causing ionisation
4. Gamma radiation has no charge / no mass, so it interacts weakly with matter and causes much less ionisation per unit distance

## Key terms

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

## Related

- [Revision notes for OCR GCSE Physics A: Gateway Science (J249)](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-alpha-radiation-is-more-7d2a078d) · Published by Druglandscape Ltd.