The count rate due to a sample of a radioactive isotope is measured for 80 minutes and recorded in the table below:
| Time (minutes) | Count rate (counts / second) |
|---|---|
| 0 | 640 |
| 20 | 450 |
| 40 | 320 |
| 60 | 225 |
| 80 | 160 |
What is the half-life of the isotope?
20 minutes20\text{ minutes}20 minutes
40 minutes40\text{ minutes}40 minutes
60 minutes60\text{ minutes}60 minutes
80 minutes80\text{ minutes}80 minutes
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.