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Cathode rays were the first to be discovered by Plucker in 1859.Its has been pointed out that when the pressure in the discharge tube is of the order 0.01mm the walls of the tube begin to glow.This greenish glow in the final stage of the gaseous discharge was soon found to be a fluorescence of the glass produced by some invisible rays emanating from the cathode.These rays were called the cathode rays and were later found to be electrons.
Properties:
1. The rays travel in straight lines.
2. The rays emerge normally from the cathode.
3. The rays can penetrate small thickness of matter such as sheets of aluminium foil.
4. The rays carry negative charge and so they deflected by electrostatic and magnetic fields.
5. Cathode rays carry momentum and K.E.
6. They ionise gases.
7. They produce fluorescence in the glass walls of the tube.
8. They produce heat when they fall upon matter.
9. When cathode rays are suddenly stopped by a target, the target becomes source of X-Rays.