Cathode ray

Cathode rays are streams of <a href="/facts/Electron/L0KBo5cW">electrons</a> observed in <a href="/facts/Vacuum_tube/VHd1BNLq">discharge tubes</a>. If an evacuated glass tube is equipped with two <a href="/facts/Electrode/251PaKX8">electrodes</a> and a <a href="/facts/Voltage/EN2po6N2">voltage</a> is applied, glass behind the positive electrode is observed to glow, due to electrons emitted from the <a href="/facts/Cathode/tqdlGayU">cathode</a> (the electrode connected to the negative terminal of the voltage supply). They were first observed in 1859 by German physicist <a href="/facts/Julius_Pl%25C3%25BCcker/QgoMT64G">Julius Plücker</a> and <a href="/facts/Johann_Wilhelm_Hittorf/V0r7228Q">Johann Wilhelm Hittorf</a>, and were named in 1876 by <a href="/facts/Eugen_Goldstein/Mz0hLqnP">Eugen Goldstein</a> Kathodenstrahlen, or cathode rays. In 1897, British physicist <a href="/facts/J._J._Thomson/Y4jyndJF">J. J. Thomson</a> showed that cathode rays were composed of a previously unknown negatively charged particle, which was later named the electron. <a href="/facts/Cathode-ray_tube/8NVGx5C7">Cathode-ray tubes</a> (CRTs) use a focused beam of electrons deflected by electric or magnetic fields to render an image on a screen.

Cathode ray open-in-new

Cathode ray