A radioactive source has a half-life of 8 days8\text{ days}8 days.
A detector near the source shows a reading of 4800 counts per second4800\text{ counts per second}4800 counts per second.
Background radiation can be ignored.
What is the reading on the detector 24 days24\text{ days}24 days later?
600 counts per second600\text{ counts per second}600 counts per second
1200 counts per second1200\text{ counts per second}1200 counts per second
1600 counts per second1600\text{ counts per second}1600 counts per second
2400 counts per second2400\text{ counts per second}2400 counts per second
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.