A researcher recorded the radiation count rate of a radioactive source with a known half-life of exactly 10.0 minutes10.0\text{ minutes}10.0 minutes. The measurements are shown in the table below:
| Time (minutes\text{minutes}minutes) | Count rate (counts per minute\text{counts per minute}counts per minute) |
|---|---|
| 000 | 520520520 |
| 10.010.010.0 | 270270270 |
| 20.020.020.0 | 145145145 |
| 30.030.030.0 | 82.582.582.5 |
State why each measured count rate is always greater than half of the previous value.
Calculate the constant level of background radiation, in counts per minute\text{counts per minute}counts per minute, present during this experiment.
144 exam-style questions on CIE IGCSE Physics 5.2.4a Half-life. Each one has a worked solution and a mark scheme showing where the marks go.