The table shows the results of an experiment to find the half-life of a radioactive substance.
| Time / s\text{s}s | Count rate from substance / counts/second\text{counts/second}counts/second |
|---|---|
| 0 | 200 |
| 40 | 160 |
| 80 | 128 |
| 120 | 100 |
| 160 | 80 |
What is the half-life of the substance?
40 seconds40\text{ seconds}40 seconds
80 seconds80\text{ seconds}80 seconds
120 seconds120\text{ seconds}120 seconds
160 seconds160\text{ seconds}160 seconds
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.