In radiotherapy, different types of radiation are used depending on the location of the cancer. To treat a certain localized internal tumour, a doctor implants tiny seeds containing an alpha-emitting isotope directly into the tumour. For a different patient with a deep brain tumour, a machine outside the body directs gamma radiation at the cancer.
Explain why the alpha source must be implanted directly inside the tumour, whereas the gamma source can be positioned outside the body.
90 exam-style questions on Edexcel GCSE Physics 6.3 Nuclear equations and decay. Each one has a worked solution and a mark scheme showing where the marks go.