NEET Physics Photo Electric Effect, X- Rays & Matter Waves NEET PYQ-Photo Electric Effect,X-Rays

  • question_answer
    A photoelectric cell is illuminated by a point source of light 1 m away. When the source is shifted to 2 m  then:                                                                                                                                                  [AIPMT 2003]

    A)              each emitted electron carries half the initial energy

    B)       number of electrons emitted is a quarter of the initial number

    C)       each emitted electron carries one quarter of the initial energy

    D)       number of electrons emitted is half the initial number

    Correct Answer: B

    Solution :

    Key Idea: Number of photoelectrons emitted per second is directly proportional to intensity of light. Intensity of light source is            
                \[I\,\,\propto \,\,\frac{1}{{{d}^{2}}}\]
                When distance is doubled, intensity becomes one fourth.
    As number of photoelectrons \[\propto \] intensity, so number of photoelectrons is quarter of the initial number.


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