A sample of a radioactive isotope has an initial emission rate of 160 counts per second160\text{ counts per second}160 counts per second and a half-life of 6 hours6\text{ hours}6 hours. How long will it take for the emission rate to fall to 20 counts per second20\text{ counts per second}20 counts per second?
6 hours6\text{ hours}6 hours
12 hours12\text{ hours}12 hours
18 hours18\text{ hours}18 hours
24 hours24\text{ hours}24 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.