Some fruit is treated with gamma rays from a cobalt-60 source to kill bacteria. This makes the fruit last longer. Some people worry that eating the treated fruit is dangerous.
Explain why the treated fruit is not radioactive.
Explain why it would be hazardous if dust containing cobalt-60 got onto the fruit before it was eaten.
Cobalt-60 has a half-life of 5.3 years. The source is replaced when its activity falls to one quarter of its original value. Calculate how long the source can be used before it is replaced.
48 exam-style questions on OCR GCSE Physics 6.2 Uses and hazards, covering 6.2.1 Contamination and irradiation, 6.2.2 Half-life and radiation hazards, 6.2.3 Medical uses of nuclear radiation, 6.2.4 Nuclear fission and chain reactions, and 6.2.5 Nuclear fusion. Each one has a worked solution and a mark scheme showing where the marks go.