KVPY Sample Paper KVPY Stream-SX Model Paper-5

  • question_answer
    A parallel beam of monochromatic radiation of cross-section area \[A(<\pi {{a}^{2}}),\] intensity I and frequency v is incident on a solid conducting sphere of work function \[{{\phi }_{0}}[hv>{{\phi }_{0}}]\] and radius 'a'. The sphere is grounded by a conducting wire. Assume that for each incident photon one photoelectron is ejected. Just after this radiation   is incident on initially uncharged sphere, the current through the conducting wire is -  

    A)        \[\frac{IAe}{hv}\]                                  

    B) \[\frac{IAe}{2hv}\]

    C) \[\frac{2IAe}{hv}\]                    

    D) None

    Correct Answer: B

    Solution :

    [A] Number of photons incident on sphere per second \[=\frac{IA}{hv}\] \[\therefore \] photo electrons ejected per second \[d=\frac{IA}{hv}\] \[\therefore \] current through conducting wire = photo current ejected from surface of sphere \[=\frac{IAe}{hv}\]

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