A radioactive source has an initial count-rate of 120 counts per minute (cpm)120\text{ counts per minute (cpm)}120 counts per minute (cpm). The half-life of the radioactive source is 15 minutes15\text{ minutes}15 minutes.
What is the count-rate of the radioactive source after 45 minutes45\text{ minutes}45 minutes?
15 cpm15\text{ cpm}15 cpm
30 cpm30\text{ cpm}30 cpm
40 cpm40\text{ cpm}40 cpm
60 cpm60\text{ cpm}60 cpm
41 exam-style questions on OCR GCSE Physics Radioactive emissions. Each one has a worked solution and a mark scheme showing where the marks go.