Internally, gamma is not as ionising as alpha or beta so there is less risk of cell damage. The source has to be very penetrating so that it can be detected outside the body or above ground. Why choose a gamma source with a short half-life? Reveal answer A leak will cause a buildup of radioactivity that can be detected above the ground. The same principle is used in leak detection of underground pipes. Arterial blockages or internal bleeds cause a build-up of radioactivity that can be easily detected outside the body. Technetium-99m, which is a gamma source with a short half-life of about six hours, is injected into blood. However, they are used mainly in medicine to monitor blood flow. They can show the movement of pollution, eg sewage or waste oil from factories. Radioactive tracers are added to liquids to show if they are flowing correctly. Blood and fluid tracersĪ tracer is something that shows how an object moves. This means the smoke alarm will not need to be changed daily. The isotope should be an alpha emitter with a long half-life. Alpha is weakly penetrating so smoke stops it, the current drops and the alarm goes off. Alpha radiation ionises the air and this allows a small current to flow between two electrodes. Smoke alarmsĪn isotope of americium which emits alpha particles is used in smoke alarms. Gamma radiation kills microbes and can be used to sterilize medical instruments and kill the bacteria on fruit and vegetables so they stay fresh longer.
Sterilizing medical instruments and prolonging the life of fruit You don’t want to keep replacing the source every few days, and a short half-life would mean that the count rate detected might be reducing if the paper stayed the same thickness.
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