Question
Cathode rays are produced when the pressure is of the order of
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Answer
(c) The air pressure inside the cathode ray tube is low. Because if we increase the pressure of gas present inside the tube then the number of atoms of the gas increases.
ie, we have $PV =nRT$
If volume and temperature are kept constant then pressure is directly proptional to n which is amount of gas in moles. If the number of atoms in the tube increases then electrons will collide with these atoms. These collisions will act as obstructions in the path of electrons thereby preventing electrons from reaching anode.
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