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NEET Sample Paper NEET Sample Test Paper-84

  • question_answer
    The threshold frequency for a photosensitive metal is \[3.3\times {{10}^{14}}Hz\]. If light of frequency \[8.2\times {{10}^{14}}Hz\]  is incident on this metal, the cut-off voltage for the photoelectric emission is nearly

    A) 2 V      

    B)                    3 V

    C) 5 V                  

    D)        1 V

    Correct Answer: A

    Solution :

    [a] \[K.E.=hv-h{{v}_{th}}=e{{V}_{0}}\,\,({{V}_{0}}=cut\,of\,voltage)\] \[\Rightarrow \]\[{{V}_{0}}=\frac{h}{e}(8.2\times {{10}^{14}}-3.3\times {{10}^{14}})\] \[=\frac{6.6\times {{10}^{-34}}\times 4.9\times {{10}^{14}}}{1.6\times {{10}^{-19}}}\approx 2\,V\].


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