Describe the experiment that led to the discovery of the electron.

The  scientist named J.J. Thomson discovered the electrons by cathode ray experiment

He gave the proof of electrons in the atom by his experiment in which he had used cathode ray tubes.These tubes are a source of cathode rays production. Cathode ray tubes are the glass tubes in which air is absent and in order to maintain this, sealing is done at the ends of the rods.

He took two electrodes, anode (with positive charge) and cathode (with negative charge). There was a high voltage across them, which caused a beam of particles to flow from cathode to anode. These rays can be detected by screening them onto phosphor film(photo sensitive material)  which is a  was set up far away from the anode. The phosphor emits light when they comes in contact with the cathode rays.

In order to test the properties of the particles, he used two oppositely-charged electric plates around the cathode ray.

He observed that the cathode rays were repelled away from the negatively-charged electric plate and attracted towards the positively-charged plate and by which he concluded that the cathode rays were composed of negatively-charged particles which were named as electrons (subatomic particle).

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