Haryana PMT Haryana PMT Solved Paper-2010

  • question_answer
    If maximum velocity with which an electron can  be  emitted  from  photo-cell  is \[4\times {{10}^{8}}cm/s,\] the stopping potential is (mass of electron \[=9\times {{10}^{-}}^{31}kg\])

    A)  30V

    B)  45V

    C)  59V

    D)  Information is insufficient

    Correct Answer: B

    Solution :

                    Given, \[{{v}_{\max }}=4\times {{10}^{8}}cm/s=4\times {{10}^{6}}m/s\] \[\therefore \] \[{{K}_{\max }}=\frac{1}{2}mc_{\max }^{2}=\frac{1}{2}\times 9\times {{10}^{-31}}\times {{(4\times {{10}^{6}})}^{2}}\]                 \[=7.2\times {{10}^{-18}}J=45eV\] Hence, stopping potential \[|{{V}_{0}}|=\frac{{{K}_{\max }}}{e}=\frac{45\,eV}{e}\]                                 \[=45V\]


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