2. Questions Bank
  3. JEE Main & Advanced
  4. Physics
  5. Photo Electric Effect, X- Rays & Matter Waves

JEE Main & Advanced Physics Photo Electric Effect, X- Rays & Matter Waves Question Bank Critical Thinking

  • question_answer
    When a point source of monochromatic light is at a distance of 0.2 m from a photoelectric cell, the cut-off voltage and the saturation current are 0.6 volt and 18 mA respectively. If the same source is placed 0.6 m away from the photoelectric cell, then                      [IIT JEE 1992; MP PMT 1999]

    A)            The stopping potential will be 0.2 V

    B)            The stopping potential will be 0.6 V

    C)            The saturation current will be 6 mA

    D)            The saturation current will be 18 mA

    Correct Answer: B

    Solution :

               Cut off voltage is independent of intensity and hence remains the same. Since distance becomes 3 times, so intensity (I) becomes \[\frac{I}{9}.\] Hence photo current also decreases by this factor i.e. becomes \[\frac{18}{9}=2\,mA.\]


You need to login to perform this action.
You will be redirected in 3 sec spinner