The count rate measured near a radioactive source drops from 1064 counts per minute to 168 counts per minute in 15 hours. The background count remains constant at 40 counts per minute.
What is the half-life of the source?
333 hours
555 hours
7.57.57.5 hours
151515 hours
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.