The table below gives the count-rate obtained from a sample of a radioactive isotope over a period of 100 minutes.
| Time / minutes | 0 | 20 | 40 | 60 | 80 | 100 |
|---|---|---|---|---|---|---|
| Count-rate / s−1\text{s}^{-1}s−1 | 600 | 356 | 212 | 125 | 74 | 44 |
From this table, estimate the half-life of the radioactive isotope.
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.