Uses of radioactivity
Smoke detectors
Smoke detectors use Americium-241, an alpha source, which detects smoke. The alpha particles move around between the two metal plates causing the air surrounding it to ionise (split into positive and negative ions). These ions are then attracted to the oppositely charged metal plates causing a current to flow. When smoke enters between the plates, some of the alpha particles are absorbed causing less ionisation to take place. This then causes a smaller current to flow, which then causes the alarm to sound.

Tracers
Radioactive also have a medical use as tracers, to see if the body is working properly. They work by either injecting or swallowing a radioactive source into a patient. As the source makes its way around the body it is followed by a radioactive detector, these readings are then converted to a TV showing where the strongest reading is coming from. Either Beta or Gamma radiation is used because they easily pass in and out of the body, and the doctors also choose things which are only radioactive for a few hours.
Thickness control
Beta radiation is used during thickness control. To do this you direct radiation through the object being made, and but a detector on the other side – which is connected to a control unit. When the detected radiation is going down, it means that the paper is coming out to thick, so the control unit make the rollers closer together to make the paper thinner. If the reading of radiation goes