# A hospital disposes of radioactive waste from a medical procedure. The waste contains a radioactive isotope with a half-life of 8 days. A radiation protection officer states that after 32 days the waste will be safe to dispose of in normal refuse. Explain what is meant by the term 'half-life' and use it to justify the officer's statement.

> WJEC GCSE Physics (Wales) — 2.8 Half-life · Explain · 4 marks

## Mark scheme (4 marks)

1. Half-life is the time taken for the activity (or count rate / number of radioactive nuclei) of a radioactive source to fall to half its original value
2. 32 days represents 4 half-lives (32 ÷ 8 = 4)
3. After each half-life the activity halves, so after 4 half-lives the activity has halved four times
4. After 4 half-lives the activity is 1/16 of the original value, so the level of radioactivity is much lower / negligible / safe

## Key terms

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

## Related

- [Revision notes for WJEC GCSE Physics (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-hospital-disposes-of-radioactive-waste-176c4a7c) · Published by Druglandscape Ltd.