A radioactive source has a half-life of 4 days. A detector near the source shows a reading of 8000 counts per minute. Background radiation can be ignored. What is the reading on the detector 12 days later?
1000 counts per minute1000\text{ counts per minute}1000 counts per minute
2000 counts per minute2000\text{ counts per minute}2000 counts per minute
2667 counts per minute2667\text{ counts per minute}2667 counts per minute
4000 counts per minute4000\text{ counts per minute}4000 counts per minute
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.