Question

Cathode rays are made up of________________ charged particle.

Answer 1

Properties of cathode rays :

• Cathode rays travel in a straight line at a high velocity and generate normally from the surface of the cathode. If an opaque object is placed in the path of cathode rays its shadow falls on the opposite side of the cathode. It shows that cathode rays travel in straight lines.
• They are a beam of minute material particles having definite mass and velocity. When a light paddle wheel is placed in the path of the cathode rays, the blades of the paddle wheel begin to rotate. This also proves that cathode rays have mechanical energy.
• They consist of negatively charged particles. When the cathode rays pass through an electric field, they bent towards the positive plate of the electric field. This indicates that cathode rays are negatively charged.
• Cathode rays can affect the photographic plate.
• The nature of cathode rays is independent of the nature of the gas used in the discharge tube or the material of the cathode.
• Cathode rays are deflected in the magnetic field also.
• If cathode rays are focused on a thin metal foil, the metal foil gets heated up to incandescence.
• When cathode rays fall on materials having high atomic mass, a new type of penetrating rays of very small wavelength are emitted which are called X - rays. Thus, investigations on cathode rays showed that these consisted of negatively charged particles.

The negatively charged particles of cathode rays were called ‘negatrons‘ by Thomson. The name negatron was changed to ‘electron‘ by Stoney.