A detector is used to monitor the emissions from a radioactive source over a period of 50 minutes.
The table shows the count rate from the source at different times.
| Time / minutes | Count rate / counts s−1\text{counts s}^{-1}counts s−1 |
|---|---|
| 0 | 800 |
| 10 | 600 |
| 20 | 450 |
| 30 | 335 |
| 40 | 250 |
| 50 | 190 |
What is the half-life of the source?
between 10 and 20 minutes
between 20 and 30 minutes
between 30 and 40 minutes
between 40 and 50 minutes
484 exam-style questions on CIE IGCSE Physics 5.2 Radioactivity, covering 5.2.1 Background radiation and measuring count rate, 5.2.2a Alpha, beta and gamma emission, 5.2.2b Deflection and ionising effects of nuclear radiation, 5.2.3a Radioactive decay, 5.2.3b Effects of decay on the nucleus and decay equations, 5.2.4a Half-life, 5.2.4b Choosing isotopes for applications, and 5.2.5 Effects of ionising radiation and safety precautions. Each one has a worked solution and a mark scheme showing where the marks go.