# A scientist is investigating the properties of alpha, beta and gamma radiation by placing different materials between a radioactive source and a detector. Describe the properties of each type of radiation, including their penetrating power and what materials are needed to stop each one.

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

> A Geiger-Müller tube is used to detect radiation from three separate radioactive sources. Each source emits only one type of radiation. When a sheet of paper is placed between the first source and the tube, the count rate drops to background level. When a 3 mm sheet of aluminium is placed between the second source and the tube, the count rate drops to background level. A thick slab of lead is needed to significantly reduce the count rate from the third source.

## Mark scheme (5 marks)

1. Alpha radiation is stopped by paper (or a few centimetres of air)
2. Beta radiation is stopped by a few millimetres of aluminium (or equivalent thin metal sheet)
3. Gamma radiation requires thick lead (or several centimetres of concrete) to significantly reduce its intensity, and cannot be completely stopped
4. Alpha particles are positively charged (and are helium nuclei / consist of 2 protons and 2 neutrons)
5. Beta particles are fast-moving electrons (negatively charged) and gamma rays are high-energy electromagnetic waves / radiation

## Key terms

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

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-scientist-is-investigating-the-properties-2caf8bad) · Published by Druglandscape Ltd.