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EAMCET Medical EAMCET Medical Solved Paper-2008

  • question_answer
    The threshold frequency for a certain metal is \[{{v}_{0}}.\]When a certain radiation of frequency \[2{{v}_{0}}\] is incident on this metal surface the maximum velocity of the photoelectrons emitted \[2\times {{10}^{6}}m{{s}^{-1}}.\]If a radiation of frequency \[3{{v}_{0}}\] is incident on the same metal surface the maximum velocity of the photoelectrons emitted (in\[m{{s}^{-1}}\]) is

    A) \[2\times {{10}^{6}}\]                                   

    B)  2\[\sqrt{2}\] \[\times {{10}^{6}}\]

    C)   4\[\sqrt{2}\]\[\times {{10}^{6}}\]                          

    D)  4\[\sqrt{3}\]\[\times {{10}^{6}}\]

    Correct Answer: B

    Solution :

                     Kinetic energy (E), \[\frac{1}{2}mv_{1}^{2}=2h{{v}_{0}}-h{{v}_{0}}=h{{v}_{0}}\] and        \[\frac{1}{2}mv_{2}^{2}=3h{{v}_{0}}-h{{v}_{0}}=2h{{v}_{0}}\] \[\therefore \]  \[\frac{1}{2}mv_{2}^{2}=2\left[ \frac{1}{2}mv_{1}^{2} \right]\] \[\Rightarrow \]               \[v_{2}^{2}=2v_{1}^{2}\] or            \[{{v}_{2}}=\sqrt{2{{v}_{1}}}\] or            \[=\sqrt{2}\times 2\times {{10}^{6}}\] \[\Rightarrow \]               \[{{v}_{2}}=2\sqrt{2}\times {{10}^{6}}m/s\]


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