The rates of emission from four radioactive sources are measured at 30-minute intervals.
Each row in the table shows the results for one of the radioactive sources.
| Source | Rate of emission at t=0t = 0t=0 (counts/s) | Rate of emission at t=30 mint = 30\text{ min}t=30 min (counts/s) | Rate of emission at t=60 mint = 60\text{ min}t=60 min (counts/s) |
|---|---|---|---|
| A | 800 | 400 | 200 |
| B | 800 | 200 | 50 |
| C | 400 | 380 | 361 |
| D | 400 | 280 | 200 |
Which source has the shortest half-life?
Source A
Source B
Source C
Source D
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.