Radioactivity

Radioactivity
Radioactivity is the spontaneous discharge of radiation, either directly from unstable atomic nuclei or as a result of a nuclear reaction. The radiation can consist of either Alpha, Beat or Gamma particles.

Alpha Particles:
Alpha particles are the heaviest and least penetrating form of ionizing radiation. They basically consist of a positively-charged nuclei of helium atoms, consisting of two protons and two neutrons. They can be stopped by clothing or a sheet of paper.

How a Smoke Alarm Works:
Americium-241, a source of Alpha particles in the radioactive sources is a smoke detector. The alpha particles ionize the molecules of the air forming ions and electrons which are attracted to a pair of charged plates separated by about a centimeter. When the ions and electrons strike the plates they provide a small amount of electricity. This amount of electricity does not alter and is monitored by the smoke alarm. When smoke particles enter the detector, those near to the radioactive source absorb many of the alpha particles before they can ionize the air between the charged plates. The number of ions and electrons between the plates reduces, thus the amount of electricity that is passed between the plates also reduces. The smoke detector notivces the decrease in current, setting off the alarm.

Beta Particles:
Gamma Radiations are of very short wavelength