Cathode rays Almost all discoveries related to particles such as electrons, ions, etc.
J.J. Thomson was the first to show, with the help of experiments with discharge tubes that electrons are same in all substances and that atom is made up of particles which are not indivisible as suggested by Dalton s atomic theory. The electrodes are made of any metal which is a good conductor, such as copper, aluminum, platinum, etc. The discharge tube has a facility to connect it to a vacuum pump. The electrodes can be connected externally to a high voltage source. The discharge tube is named so because of the gaseous discharge that takes place between the two electrodes.