A radioactive source has a half-life of 5.0 years5.0\text{ years}5.0 years. It currently emits radiation at a rate of 900 particles per second900\text{ particles per second}900 particles per second. At what rate was it emitting radiation 15.0 years15.0\text{ years}15.0 years earlier?
112.5 particles per second112.5\text{ particles per second}112.5 particles per second
1800 particles per second1800\text{ particles per second}1800 particles per second
3600 particles per second3600\text{ particles per second}3600 particles per second
7200 particles per second7200\text{ particles per second}7200 particles per second
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.