A patient is injected with a radioactive tracer to check how well their kidneys are working. An external radiation detector is placed over the kidneys to measure the count rate of the radiation emitted.
Explain why a source that emits gamma radiation is used rather than one that emits alpha radiation.
The radioactive isotope used has a half-life of 6 hours6\text{ hours}6 hours. When first injected, the detector measures a count rate of 240 counts per second240\text{ counts per second}240 counts per second from the tracer. Calculate the count rate measured by the detector after 18 hours18\text{ hours}18 hours, assuming background radiation is negligible. Show your working.
Explain why it is important that the radioactive isotope used for this medical diagnosis has a short half-life of only a few hours, rather than a long half-life of several years.
16 exam-style questions on AQA GCSE Physics 4.3 Hazards and uses of radioactive emissions and of background radiation, covering 4.3.1 Background radiation, 4.3.2 Different half-lives of radioactive isotopes, and 4.3.3 Uses of nuclear radiation. Each one has a worked solution and a mark scheme showing where the marks go.