# Smoke detectors in homes use a radioactive source that emits alpha particles. Explain why alpha particles are suitable for use inside a smoke detector in a home, and why the detector does not pose a significant radiation hazard to the people living there.

> Eduqas GCSE Physics — 9.3 Hazards and uses of radioactive emissions · Explain · 4 marks

> A smoke detector contains a small amount of a radioactive source. Under normal conditions, alpha particles ionise the air inside the detector, allowing a small electric current to flow. When smoke enters the detector, the current is interrupted and the alarm sounds.

## Mark scheme (4 marks)

1. Alpha particles are highly ionising, so they can ionise the air inside the detector effectively to maintain the current.
2. Alpha particles have a very short range in air (a few centimetres), so they cannot travel far enough to reach people in the room.
3. Alpha particles are also stopped by the casing of the detector, so they cannot escape to irradiate people nearby.
4. If a more penetrating radiation (beta or gamma) were used instead, it would pass through the casing and through the body, posing a greater hazard to the occupants.

## Key terms

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

## Related

- [Revision notes for Eduqas GCSE Physics](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/smoke-detectors-in-homes-use-a-54342061) · Published by Druglandscape Ltd.