When a radioactive isotope is set up close to a radiation detector, a count rate of 80,000 counts/s80,000\text{ counts/s}80,000 counts/s is initially obtained. The table shows the count rate from the isotope over a three-day period:
| Time (days) | Count rate (counts/s) |
|---|---|
| 0 | 80,000 |
| 1 | 61,000 |
| 2 | 46,000 |
| 3 | 35,000 |
What is the half-life of the isotope?
less than 1 day
more than 1 day but less than 2 days
more than 2 days but less than 3 days
more than 3 days
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.