Which statement correctly defines the half-life of a radioactive source?
The time taken for the activity of the source to fall to half of its original value.
Half the time taken for the activity of the source to fall to zero.
The time taken for all the radioactive nuclei in the source to decay.
The time taken for a single nucleus to split into two smaller nuclei.
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.