2. Background Radiation Background radiation is radioactivity that is always present Background radiation is caused by radioactive substances in rocks and soil and by cosmic rays. Some background radiation comes from waste products and man made sources e.g. waste from: industry; hospitals.

3. Radioactive gamma ray sources can be used as tracers to track dispersal of waste; to find leaks/blockages in underground pipes; to find the route of underground pipes. radioactive material is put into pipe; a gamma source used so that it can penetrate to the surface; the progress is tracked with a detector above the ground; a leak or blockage is shown by a reduction or no radioactivity after this point

4. Americium-241 emits alpha particles that ionise the air molecules around the alarm. The charged air molecules conduct electricity so a small current flows inside the alarm. When smoke enters the alarm alpha particles are absorbed. This makes the current inside the alarm fall and set off a ringing sound. Alpha emitters must be used for smoke detectors since only alpha particles ionise air and are stopped by smoke. Gamma rays and beta particles easily pass through air without causing ionisation. Alpha sources can be used in smoke detectors