Discovery:
The electron is the lightest particle to exist and carries a negative charge. It was first discovered by Goldstein in 1886 and was further investigated by J.J. Thomson in 1897.
Experimental design:
Experimental explanation:
The apparatus shown above is a discharge tube. Its consists of a glass tube with two metal electrodes connected to a high voltage source and also has a vacuum pump to generate a low pressure environment of air inside the tube. Once the voltage is provided a streak of light is observed that travels towards the anode which has positive charge. This causes a glow on the wall of the anode side.
Thomson stated that since these rays were deflected towards positive plate in an electric and magnetic field they should have opposite charge for attraction to happen. These rays were then classified as having negative charge and the particles were given the name of ‘electron’.
Cathode rays (Electrons) properties:
They travel in straight line towards anode
They produce sharp shadow of an opaque object placed in their path.
They have negative charge and bend towards positive plate in electric and magnetic field.
When they strike with glass and other material they cause material glow.
The which is charge to mass ratio is coulomb per gram which is same for all electrons, no matter what gas is present in discharge tube.
They can produce mechanical pressure indicating they possess kinetic energy.
