Question

What are the cathode rays? How are these rays formed?

Answer 1

• A cathode ray is a beam of electrons in a vacuum tube travelling from the negatively charged electrode (cathode) at one end to the positively charged electrode (anode) at the other, across a voltage difference between the electrodes. They are also called electron beams.

• Cathode rays are nothing but the beam of electrons observed in vacuum tubes. When a discharge tube or evacuated glass tube is facilitated with two electrodes positive (anode) and negative (cathode) and with an applied voltage, due to the emission of electrons from and travelling in the perpendicular to the cathode, the glass opposite of negative electrode is observed to glow.
• Cathode rays are emitted by the cathode in a vacuum tube and this is done by using Crookes tube or now modern vacuum tubes (or discharge tubes).
• The high electric potential is applied between the anode and cathode to ionize the residual gas in the tube.
• The ions are accelerated by electric field and they collided with cathode which released electrons.
• As electrons are negatively charged they are repelled by the cathode and are attracted towards the anode.
• Electrons travel in a straight line in the empty tube. They have high velocities and are colourless (invisible).