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

  • question_answer
    When intensity of incident light increases:                                                                           [AIPMT 1999]

    A)  photo-current increases

    B)                   photo-current decreases

    C)  kinetic energy of emitted photoelectrons increases

    D)       kinetic energy of emitted photoelectrons decreases

    Correct Answer: A

    Solution :

    According to Einstein's theory of photoelectric effect a single incident photon ejects a single electron. Therefore, when intensity increases, the number of incident photons increases, so number of ejected electrons increases, hence, photocurrent increases.
    Now, maximum energy of electron \[=\frac{1}{2}mv_{\max }^{2}\] and \[\frac{1}{2}mv_{\max }^{2}=e{{V}_{0}},\] where \[{{V}_{0}}\] is stoping potential
    Thus, the maximum kinetic energy of the electrons does not depend upon the intensity of the incident rays, because the stopping is not affected by the increase of the intensity of rays. Hence, options  and  are wrong.


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