Properties of Cathode rays
Cathode rays have the following properties:
i. They travel in straight lines.
ii. Cathode rays possess momentum and kinetic energy.
iii. Cathode rays produce heat, when allowed to fall on matter.
iv. Cathode rays produce fluorescence when they strike a number of crystals, minerals and salts.
v. When cathode rays strike a solid substance of large atomic weight, X-rays are produced.
vi. Cathode rays ionize the gas through which they pass.
vii. Cathode rays affect the photographic plates.
viii. The cathode rays are deflected from their straight line path by both electric and magnetic fields. The direction of deflection shows that they are negatively charged particles.
ix. Cathode rays travel with a velocity upto (1/10)th of the velocity
x. of light.
xi. Cathode rays comprises of electrons which are fundamental constituents of all atoms.
Extra Notes :
Extra Notes :
When the pressure of the gas inside the discharge tube is reduced by working the vacuum pump, to about 110 mm of Hg, no discharge occurs through the tube. At a pressure of about 100 mm of Hg, the discharge of electricity through the gas begins and irregular streaks of light appear, accompanied by a crackling sound. As the pressure is reduced to the order of 10 mm of Hg, the irregular streaks broaden out into a luminous column extending from the anode, almost upto the cathode. This column is known as the positive column. With further reduction in pressure to around 0.01 mm of Hg, the positive column disappears and Crooke's dark space fills the whole tube. At this stage, the walls of the glass tube fluoresce with green colour. This greenish glow in the final stage of the gaseous discharge is found to be a fluorescence of the glass produced by some invisible rays emanating from the cathode (shown in the wrapper). These rays are called cathode rays and are found to be electrons.