AIIMS AIIMS Solved Paper-2004

  • question_answer
    A photon of energy 4 eV is incident on a metal surface whose work function is 2 eV. The minimum reverse potential to be applied for stopping the emission of electrons is:

    A) 2V       

    B)                                       4 V                         

    C)       6 V                         

    D)       8 V

    Correct Answer: A

    Solution :

                    Key Idea: Kinetic energy of photoelectron is \[e{{V}_{0}}\] where \[{{V}_{0}}\] is stopping potential. From Einsteins photoelectric equation \[{{E}_{k}}=\frac{1}{2}mv_{\max }^{2}=hv-W\] where \[{{E}_{k}}\] is maximum kinetic energy of electron, v is frequency and W is work function. \[\therefore \]    \[\frac{1}{2}mv_{\max }^{2}=4eV-2eV=2eV\] but \[\frac{1}{2}mv_{\max }^{2}=e{{V}_{0}}\] where \[{{V}_{0}}\] is stopping potential. Thus,      \[e{{V}_{0}}=2eV\] \[\Rightarrow \]  \[{{V}_{0}}=2V\]


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