# Americium-241 is used in smoke alarms. It is an alpha emitter with a half-life of 432 years. Explain why americium-241 is a suitable radioactive isotope for use in a smoke alarm inside a home.

> AQA GCSE Physics (8463) — 4.4.3 Hazards and uses of radioactive emissions and of background radiation (Phys only) · Explain · 4 marks

## Mark scheme (4 marks)

1. Alpha radiation is weakly penetrating / travels only a few centimetres in air
2. So the alpha radiation does not reach the occupants of the home / poses minimal radiation risk to people nearby
3. The long half-life means the activity remains roughly constant over many years / the source does not need to be replaced
4. The activity / count-rate is low enough that it does not present a significant hazard during normal use

## Key terms

- [half-life](https://www.gradenine.co.uk/glossary/half-life)

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Source: [GradeNine](https://www.gradenine.co.uk/q/americium-241-is-used-in-smoke-alarms-7b480e33) · Published by Druglandscape Ltd.