A sample of a radioactive isotope is monitored in a laboratory. The count rate is measured every 4 hours, and the results are shown in the table below.
| Time / hours | 0 | 4 | 8 | 12 | 16 | 20 | 24 | 28 |
|---|---|---|---|---|---|---|---|---|
| Count rate / cpm | 4000 | 2800 | 2000 | 1400 | 1350 | 710 | 500 | 350 |
One of the readings is incorrect due to an experimental error.
Identify the anomalous reading in the table and estimate what the correct count rate should be for that time.
Determine 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.