A student measures the count rate from a radioactive source in a laboratory. The results are recorded in the table below:
| Time / minutes | Count rate / (counts / s) |
|---|---|
| 0 | 135 |
| 1.0 | 110 |
| 2.0 | 91 |
| 3.0 | 75 |
| 4.0 | 63 |
The average background radiation in the laboratory is 15 counts/s15\text{ counts/s}15 counts/s.
What is the half-life of the source?
1.0 minute1.0\text{ minute}1.0 minute
2.0 minutes2.0\text{ minutes}2.0 minutes
3.0 minutes3.0\text{ minutes}3.0 minutes
4.0 minutes4.0\text{ minutes}4.0 minutes
144 exam-style questions on CIE IGCSE Physics 5.2.4a Half-life. Each one has a worked solution and a mark scheme showing where the marks go.