A hospital uses radioactive isotopes in two ways: to image internal organs and to sterilise surgical equipment. Explain why different types of nuclear radiation are chosen for each of these two uses, referring to the penetrating power and ionising ability of the radiation in each case.

1. Gamma rays are used for sterilising surgical equipment because they have a very high penetrating power, allowing them to pass through the packaging and the equipment itself.
2. The same high penetrating power makes gamma rays suitable for imaging internal organs, as they can travel through the body and reach the target tissues.
3. Gamma rays have a relatively low ionising ability compared with alpha or beta particles, which means they cause less damage to surrounding healthy cells during imaging.
4. Alpha particles (and to a lesser extent beta particles) cannot penetrate the skin or even a few millimetres of material, so they would be ineffective for either sterilisation or imaging.
5. Because alpha particles are the most strongly ionising, using them inside the body would cause extensive cell damage and mutations, making them unsuitable for medical imaging.