The Collaborative International Dictionary
Alpha rays \Alpha rays\ (Physics & Chem.) Rays of relatively low penetrating power emitted by radium and other radioactive substances, and shown to consist of positively charged alpha particles (helium nuclei) having enormous velocities but small masses. They are slightly deflected by a strong magnetic or electric field. Compare beta ray and gamma ray. Because the rays penetrate only a small distance in dense matter such as living tissue, small pellets of radioactive substances emitting alpha rays have been used to cause local destruction of tissue, as in cancer therapy.
n. (alpha ray English)
Usage examples of "alpha rays".
That had been preceded by the discovery of radio waves and cathode rays, and it was to be rapidly followed by the discovery of alpha rays, beta rays, and gamma rays.
Instead of being activated by light, zinc sulfide crystals are stimulated by alpha rays, supplied by trace amounts of radium -- no more than two parts per million -- mixed into the pigment compounds.