<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2011) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2011) (Learn how and when to remove this template message) </Td> </Tr> <P> Cathode rays (also called an electron beam or e-beam) are streams of electrons observed in vacuum tubes . If an evacuated glass tube is equipped with two electrodes and a voltage is applied, glass behind the positive electrode is observed to glow, due to electrons emitted from and traveling away from the cathode (the electrode connected to the negative terminal of the voltage supply). They were first observed in 1869 by German physicist Johann Wilhelm Hittorf, and were named in 1876 by Eugen Goldstein Kathodenstrahlen, or cathode rays . In 1897, British physicist J.J. Thomson showed that cathode rays were composed of a previously unknown negatively charged particle, which was later named the electron . Cathode ray tubes (CRTs) use a focused beam of electrons deflected by electric or magnetic fields to create the image on a television screen . </P> <P> Cathode rays are so named because they are emitted by the negative electrode, or cathode, in a vacuum tube . To release electrons into the tube, they first must be detached from the atoms of the cathode . In the early cold cathode vacuum tubes, called Crookes tubes, this was done by using a high electrical potential between the anode and the cathode to ionize the residual gas atoms in the tube; the ions were accelerated by the electric field and released electrons when they collided with the cathode . Modern vacuum tubes use thermionic emission, in which the cathode is made of a thin wire filament which is heated by a separate electric current passing through it . The increased random heat motion of the filament knocks electrons out of the surface of the filament, into the evacuated space of the tube . </P>

Who discovered the electron using a cathod ray