A radioactive source has a half-life of 15 minutes.
A detector near the source shows a reading of 4800 counts per second.
Background radiation can be ignored.
What is the reading on the detector 1.0 hour later?
300300300 counts per second
600600600 counts per second
120012001200 counts per second
240024002400 counts 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.