AMU Medical AMU Solved Paper-2012

  • question_answer
    The threshold frequency for a certain photosensitive metal is \[{{v}_{0}}\]. When it is illuminated by light of frequency \[v=2{{v}_{0}}\], the maximum velocity of photoelectrons is \[{{v}_{0}}\]. What will be the maximum velocity of the photoelectron when the same metal is illuminated by light of frequency \[v=5{{v}_{0}}\]?

    A)  \[\sqrt{2}\,{{v}_{0}}\]                  

    B)  \[2\,{{v}_{0}}\]

    C)  \[2\sqrt{2}\,{{v}_{0}}\]                

    D)  \[4\,{{v}_{0}}\]

    Correct Answer: B

    Solution :

                    \[{{v}_{\max }}=\sqrt{\frac{2h\,(v-{{v}_{0}})}{m}}\]                 \[v=2{{v}_{0}}\] \[\therefore \]  \[{{v}_{\max }}={{v}_{0}}=\sqrt{\frac{2h\,(2{{v}_{0}}-{{v}_{0}})}{m}}\]                 \[{{v}_{0}}=\sqrt{\frac{2h{{v}_{0}}}{m}}\] Again     \[v=5{{v}_{0}}\] \[\therefore \] The maximum velocity of the photoelectron                 \[{{v}_{\max }}=\sqrt{\frac{2h(5{{v}_{0}}-{{v}_{0}})}{m}}\]                                 \[=\sqrt{\frac{2h4{{v}_{0}}}{m}}\]                                 \[=2\sqrt{\frac{2h{{v}_{0}}}{m}}=2\,{{v}_{0}}\]


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