Cathode rays, discovered by Sir Willium Crooke are the stream of electrons. They may be given by using a discharge tube containing gas at a low pressure of the order of 10-2 mm of Hg. At that pressure the gas particles ionize and the emitted electrons travel in the direction of positive potential of anode. The positive ions touch the cathode to make emission of electrons from cathode. These electrons also go in the direction of anode. Therefore the cathode waves in the discharge tube are the electrons given because of ionization of gas and that emitted by cathode because of collision of positive ions.