2. Sample Papers
  3. JEE Main & Advanced

JEE Main & Advanced Sample Paper JEE Main - Mock Test - 31

  • question_answer
    The threshold frequency for a certain metal is \[{{V}_{0}}\]when light of frequency \[v=2{{v}_{0}}\] is incident on it. The maximum velocity of photoelectrons is \[4\times {{10}^{6}}m/s.\] If the frequency of incident radiation is increase to\[5\,{{v}_{0}}\], the maximum velocity of photo electrons in m/s will be.

    A) \[\frac{4}{5}\times {{10}^{6}}\]        

    B)        \[2\times {{10}^{6}}\]

    C) \[8\times {{10}^{6}}\]   

    D)        \[2\times {{10}^{7}}\]

    Correct Answer: C

    Solution :

      [c] \[\frac{1}{2}m{{V}^{2}}=h\left( v-{{v}_{0}} \right)\] Case I: v = 2vo \[\frac{1}{2}m{{V}_{1}}^{2}=h{{v}_{0}}\]           ...(1) for \[V=5{{v}_{0}}\] \[\frac{1}{2}m{{V}_{2}}^{2}=4h{{v}_{0}}\]         ...(2) (2)\[\div \](1) \[{{V}_{2}}^{2}=4{{V}_{1}}\] or \[{{V}_{2}}=2{{V}_{1}}\] \[=2\times 4\times {{10}^{6}}=8\times {{10}^{6}}\]    


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