• # 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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