A radioactive substance has a half-life of 8 hours8\text{ hours}8 hours. It has an initial rate of emission of 240 counts per second240\text{ counts per second}240 counts per second. How long will it take for this rate of emission to fall to 30 counts per second30\text{ counts per second}30 counts per second?
3 hours3\text{ hours}3 hours
16 hours16\text{ hours}16 hours
24 hours24\text{ hours}24 hours
64 hours64\text{ hours}64 hours
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.