Cathode Rays


 
 
Concept Explanation
 

Cathode Rays

Cathode Rays: The phenomena observed under reduced pressure and high voltage depends upon the nature of the gas in the tube. It was discovered by JJ Thomson.

  • When the pressure of the gas in the discharge tube is at atmospheric pressure and a high voltage is applied across the electrodes, nothing noticeable happens. But, as the pressure is lowered and/or the voltage is increased, sparking, or irregular streaks of light are seen in the tube.
  • When the pressure of the gas is lowered to about 10 mm of mercury, the irregular streaks of light become a continuous column of light that glows. The column starts from the anode and reaches almost up to the cathode. This column is called the positive column or cathode rays. The colour of the column of light depends on the nature of the gas taken. In case of air, the colour is reddish, and for carbon dioxide it is bluish.
  • Sample Questions
    (More Questions for each concept available in Login)
    Question : 1

    Which of the following statement / statements are correct :

    (a) The Cathode Rays are also known as positive column.

    (b) The Cathode Rays is the phenomena observed under reduced pressure and high voltage depends upon the nature of the gas in the tube.

    (c) The Cathode Rays is the phenomena observed under reduced pressure and low voltage depends upon the nature of the gas in the tube.

    Right Option : A
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    Explanation
    Question : 2

    When the pressure of the gas in the discharge tube is at atmospheric pressure and a high voltage is applied across the electrodes, nothing noticeable happens. But, as the pressure is ____________  or the voltage is __________, sparking, or irregular streaks of light are seen in the tube.

    Right Option : A
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    Explanation
    Question : 3

    Which of the following  statement / statements are correct :

    (a) The Cathode Rays is the phenomena observed under reduced pressure and high voltage depends upon the nature of the gas in the tube.

    (b) The Cathode Rays is the phenomena observed under reduced pressure and low voltage depends upon the nature of the gas in the tube.

    (c) The Cathode Rays is the phenomena observed under reduced pressure and normal voltage depends upon the nature of the gas in the tube.

    Right Option : A
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    Explanation
     
     


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