What is meant by the activity of a radioactive source?
the total number of unstable nuclei remaining in the sample
the average energy released during each nuclear decay
the number of nuclear decays occurring per unit time
the time required for half of the unstable nuclei to decay
120 exam-style questions on CIE IGCSE Physics 5.2.3a Radioactive decay. Each one has a worked solution and a mark scheme showing where the marks go.