Beta radiation is the emission of an electron from the nucleus of a radioactive isotope. This electron comes from one of the neutrons in an unstable nucleus. The weak nuclear force is involved, and the neutron is converted into a proton when the beta particle is emitted. This produces an isotope of the next element in the periodic table, a process known as transmutation. The emitted beta particle travels through air at close to the speed of light. However, it can be stopped by a sheet of aluminum foil greater than 0.12 in (3 mm) thick.

When French physicist Henri Becquerel (1852-1908) first discovered the property of radioactivity in 1896, he did not know that radiation consists of particles as well as energy. Beginning in 1898, Ernest Rutherford (1871-1937) conducted experiments to determine the nature of this radiation. One experiment demonstrated that the radiation actually consisted of three different types...