|1996 : the electron is discovered by J.J. Thomson|
Vaccum was made In Thomson's cathode ray tube. The cathode C was set to a negative voltage of a few hundred volts, the anode beeing grounded. Cathodic rays moved towards the anode passing through two collimators S in a straight line and hit the tube bottom at the point O. By applying an electric field between the two plates P1 and P2 cathodic rays were deflected along the path indicated in red. They were also deflected by the magnetic field of a coil (blue line) . From these observations and by measuring these deflections, Thomson was able to deduce the corpuscular nature of cathodic rays and identify them with tiny particles he dubbed electrons.