Which statement correctly describes the term half-life for a radioactive isotope?
The time taken for the number of unstable nuclei in a sample to decrease to a quarter of its original value.
The time taken for the activity of a sample to decrease to half of its initial value.
Half of the time required for all the radioactive nuclei in the sample to decay completely.
The average lifetime of a single radioactive nucleus.
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.