Question
What are cathode rays? How are these rays formed?
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Answer
Cathode rays are the beam of electrons which travel from the negatively charged end (i.e. cathode to anode) of a vacuum tube, across a voltage difference between the electrodes placed at each end. Formation of cathode rays: Generally gases are poor conductors of electricity. However, when a high voltage charge from an induction coil is applied to tubes filled with gases at very low pressure (0.01 mm of mercury), the gases become good conductors of electricity and begin to flow in the form of rays. These rays are called cathode rays and they travel from the cathode towards the anode. 
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