87. How are cathode rays produced? Explain briefly their important properties.

Production of cathode rays: When a current of high voltage (10000 volts) is passed through a gas or air kept at a very low pressure (0.01 -0.03 mm) contained in a discharge tube, blue rays are seen emerging from the cathode which produce a fluorescence on the walls of the discharge tube. These rays are called cathode rays.

Properties of cathode rays:
1. Cathode rays travel in a straight line.
2. Cathode rays rotate the light paddle wheel when placed in their path. This shows that these rays consist of material particles having both mass and velocity.
3. Cathode rays produce green fluorescence upon striking glass or certain other materials.
4. When cathode rays are allowed to strike on a piece of metal foil, it becomes hot which shows that these rays produce heating effect.
5. These rays ionise the gas through which they pass.
6. These rays produce X-rays when they strike against hard metals such as tungsten.
7. When an electric or magnetic field is applied on the cathode rays, they are deflected from their straight path towards the positive plate of the electric field. This shows that cathode rays are negatively charged particles. These particles were named electrons.