An experiment is performed to measure the radiation from a radioactive source. The source has a half-life of 12 minutes12\text{ minutes}12 minutes.
The source is placed close to a detector connected to a counter. The average background count rate is 40 counts/minute40\text{ counts/minute}40 counts/minute.
At the start of the experiment, the total count rate recorded by the counter is 1640 counts/minute1640\text{ counts/minute}1640 counts/minute.
What is the total count rate recorded by the counter 24 minutes24\text{ minutes}24 minutes later?
400 counts/minute400\text{ counts/minute}400 counts/minute
410 counts/minute410\text{ counts/minute}410 counts/minute
440 counts/minute440\text{ counts/minute}440 counts/minute
840 counts/minute840\text{ counts/minute}840 counts/minute
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.