Question

(a) What is the nature of charge on cathode rays?

(b) State the properties of cathode rays.

Answer 1

(a) Cathode rays are negatively charged as they consist of negatively charged particles called electrons.

(b) Properties of cathode rays:

• They travel from the cathode to the anode in straight lines.
• They cause a greenish yellow fluorescence on a soda-glass screen placed in the tube.
• They are affected by an electric field, i.e. they are inflected towards the positive field and deflected from the negative field. This shows that they carry a negative charge.
• When a beam of cathode rays is made to fall upon hard metallic targets like tungsten, X rays are produced.
• They penetrate matter.
• They cause ionisation of the gas through which they pass.
• The ratio of the charge (s) to mass (m) of the particles constituting cathode rays remains the same (e/m = $1.76\times 1011coulomb/kg$ irrespective of the nature of the gas taken and of the metal forming the cathode.
• They produce the shadow of an opaque object placed in their path and make a light paddle wheel rotate.