Electron beam being deflected by a magnet. The electron beam comprises a stream of negatively-charged particles crossing the cathode ray tube from left to right, causing a plate covered with phosphor to glow green. When the demonstrator moves a magnet close to the beam, it deflects downwards, as the field repels the charged particles. The deflection of a beam of electrons like this is the basis for cathode ray tube displays, which were used in televisions and other devices until the development of cheaper, lighter LCD and plasma screen technologies. The discovery of cathode rays led to the discovery of the electron itself by JJ Thomson in 1897, for which he won the 1096 Nobel Prize for Physics.