BHU PMT BHU PMT (Mains) Solved Paper-2011

  • question_answer
    A certain metal when irradiated by light \[(v=3.2\times {{10}^{16}}Hz)\]emits photoelectrons with twice kinetic energy as did photoelectrons when the same metal is irradiated by light\[(v=2.0\times {{10}^{16}}Hz)\]. Then\[{{v}_{0}}\]of metal is

    A)  \[1.2\times {{10}^{14}}Hz\]                       

    B)  \[8\times {{10}^{15}}Hz\]

    C)  \[1.2\times {{10}^{16}}Hz\]                       

    D)  \[4\times {{10}^{12}}Hz\]

    Correct Answer: B

    Solution :

    Sol.         \[K{{E}_{1}}=h{{v}_{1}}-h{{v}_{0}}\] \[K{{E}_{2}}=h{{v}_{2}}-h{{v}_{0}}\] \[\because \]     \[K{{E}_{1}}=2-K{{E}_{2}}\] \[\therefore \]  \[h{{v}_{1}}-h{{v}_{0}}=2(h{{v}_{2}}-h{{v}_{0}})\]                 \[h{{v}_{0}}=2h{{v}_{2}}-h{{v}_{1}}\]                 \[{{v}_{0}}=2{{v}_{2}}-{{v}_{1}}\]                 \[=2(2\times {{10}^{16}})-(3.2\times {{10}^{16}})\]                 \[=0.8\times {{10}^{16}}Hz\] \[=8\times {{10}^{15}}Hz\]


You need to login to perform this action.
You will be redirected in 3 sec spinner