IV.

History

British physicist Ernest Rutherford discovered beta radiation in 1899. While studying the element uranium, Rutherford observed two different types of emission, which he called alpha and beta rays. Alpha radiation had a positive electric charge and did not penetrate deeply into metal foil (see Alpha Particle). The beta radiation Rutherford observed was negatively charged and penetrated farther into foil. Based on his observations, Rutherford concluded that the decay of atoms produced radioactivity. British physicist Sir Joseph John Thomson had already discovered the electron in 1897, but neither Rutherford nor Thompson connected the discoveries. French physicist Antoine Becquerel identified the negative beta particle with the electron in 1899, shortly after Rutherford’s discovery.

Many naturally occurring elements emit beta particles, so the particles are relatively easy to study. In some of the most interesting work on beta particles, scientists study the range of energies beta particles can have and the effects of beta particles on human tissue.