# A technician works in a nuclear research facility and is required to handle different radioactive sources. Explain why alpha-emitting sources are considered more dangerous when inhaled or ingested, but less dangerous when the source is held a short distance away from the body.

> Pearson Edexcel International GCSE Physics (4PH1) — 7.2 Radioactivity · Explain · 4 marks

> Radioactive sources emit alpha particles, beta particles, or gamma rays. Each type of radiation has different properties that affect how hazardous it is to the human body depending on the situation.

## Mark scheme (4 marks)

1. Alpha particles are highly ionising, so inside the body they cause significant damage to cells / DNA / tissues.
2. When inhaled or ingested, the source is inside the body so the alpha particles reach living cells / organs directly.
3. Alpha particles are weakly penetrating / can be stopped by a few centimetres of air, so they cannot reach the body from a short distance outside.
4. Therefore, when the source is held a short distance away, the alpha particles are absorbed by the air before reaching the body, causing no irradiation / no harm to the technician.

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- [Revision notes for Pearson Edexcel International GCSE Physics (4PH1)](https://www.gradenine.co.uk/learn)
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