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JEE Main & Advanced Sample Paper JEE Main Sample Paper-27

  • question_answer
    When a monochromatic point source of light is at a distance \[0.2\] m from a photoelectric cell, the saturation current and cut-off voltage are \[12.0\] mA and \[0.5\] V. If the same source is placed \[0.4\] m away from the photoelectric cell, then the saturation current and the stopping potential respectively are:

    A)  4 mA and IV                

    B)  12 mA. and IV

    C)  3 mA and IV                

    D)  3mA and 0.5V

    Correct Answer: D

    Solution :

    Inverse Square Law, \[I\propto \frac{1}{{{d}^{2}}}\] \[12\,\propto \frac{1}{{{(0.2)}^{2}}}\,\,\,or\,\,I\,\propto \,\frac{1}{{{(0.2)}^{2}}}\] \[\therefore \,\,\frac{I}{12}\,=\frac{{{(0.2)}^{2}}}{{{(0.4)}^{2}}}\,=\frac{1}{4}\,\Rightarrow I=\frac{12}{4}\,=3\,mA\] Stopping potential will be same because frequency of source and work function of material is same.


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