# Radioactive sources are used in industry to measure the thickness of metal sheets during manufacturing. A beta source is placed on one side of the metal sheet and a detector is placed on the other side. Explain why a beta source is chosen for this process, rather than an alpha source or a gamma source.

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

> In a metal sheet factory, the thickness of steel sheets must be carefully controlled. A radioactive source and detector are used to monitor the thickness automatically.

## Mark scheme (4 marks)

1. Alpha particles would be stopped/absorbed by the metal sheet, so none would reach the detector
2. Beta particles can penetrate the metal sheet but are partially absorbed by it
3. The amount of beta radiation reaching the detector depends on the thickness of the sheet
4. Gamma radiation would pass straight through the metal with very little absorption, so the detector reading would not change significantly with thickness

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/radioactive-sources-are-used-in-industry-e88b5f21) · Published by Druglandscape Ltd.