CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2006

  • question_answer
    In a photoelectric effect measurement, the stopping potential for a given metal is found to be\[{{V}_{0}}\]volt when radiation of wavelength\[{{\lambda }_{0}}\]is used. If radiation of wavelength\[2{{\lambda }_{0}}\]is used with the same metal then the stopping potential (in volt) will be:

    A)  \[\frac{{{V}_{0}}}{2}\]                  

    B)  \[2{{V}_{0}}\]

    C)  \[{{V}_{0}}+\frac{hc}{2e{{\lambda }_{0}}}\]       

    D)         \[{{V}_{0}}-\frac{hc}{2e{{\lambda }_{0}}}\]

    E)  \[{{V}_{0}}\]

    Correct Answer: D

    Solution :

    From Einsteins photoelectric equation \[e{{V}_{0}}=\frac{hc}{{{\lambda }_{0}}}-{{W}_{0}}\] \[eV=\frac{hc}{2{{\lambda }_{0}}}-{{W}_{0}}\] Subtracting \[e({{V}_{0}}-V)-\frac{hc}{{{\lambda }_{0}}}\left[ 1-\frac{1}{2} \right]=\frac{hc}{2{{\lambda }_{0}}}\] Or           \[V={{V}_{0}}-\frac{hc}{2e{{\lambda }_{0}}}\]


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