A radioactive isotope has a half-life of 15 days15\text{ days}15 days.
It initially emits radiation at a rate of 800 counts per second800\text{ counts per second}800 counts per second.
How long does it take for the rate of emission to fall to 100 counts per second100\text{ counts per second}100 counts per second?
5 days5\text{ days}5 days
30 days30\text{ days}30 days
45 days45\text{ days}45 days
120 days120\text{ days}120 days
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.