2. Radioactivity and radioisotopes Applications of Radioactivity Radioactive tracers

3. Beneficial uses of radioactivity Controlled radioactivity can be used to (click on the picture for more information): Kill cancer cells Sterilize food and medical equipment Find leaks in pipes Control thickness in industry Check organs work properly

4. Tracers in medicine The patient drinks some iodine 131. A  -probe measures the amount of radioactive iodine the thyroid gland takes in to check it works properly. N.B. All isotopes taken into the body should be GAMMA or BETA sources and never ALPHA. Explain why… These tracers must have short half-life

5. Tracers in industry Why don’t they use  or  ? These tracers must have short half-life

6. Gamma source Curing cancer High doses of gamma rays will kill all living cells Gamma rays can be directed only at the cancer cells to cure the cancer Sterilizing food For the same reason gamma rays can be used to kill the microbes in food and medical instruments. UNSTERILIZEDSTERILIZED

7. Thickness control in industry In paper mills, the thickness of the paper can be controlled by measuring how much beta radiation passes through the paper to a Geiger counter. The counter controls the pressure of the rollers to give the correct thickness. With paper, or plastic, or aluminium foil, b rays are used, because a will not go through the paper. We choose a source with a long half-life so that it does not need to be replaced often.