JCECE Engineering JCECE Engineering Solved Paper-2002

  • question_answer
    The work function of a metal is \[1\,\,eV\]. If \[3000\overset{\text{o}}{\mathop{\text{A}}}\,\] wavelength light is incident, the value of stopping voltage is:

    A) \[1\,\,V\]                                            

    B) \[3.75\,\,V\]

    C)  \[3.2\,\,V\]                       

    D)  \[0.75\,\,V\]

    Correct Answer: B

    Solution :

    Key Idea: Use following formula to find the value of stopping potential.                 \[{{W}_{0}}=e{{V}^{0}}=\frac{hc}{\lambda }\] where\[c=velocity\,\,of\,\,light=3.0\times {{10}^{8}}m/s\] \[\lambda =wavelength=3000{\AA}=3000\times {{10}^{-10}}m\] \[{{W}_{0}}=\]work function\[=1\,\,eV\]                 \[{{W}_{0}}=\frac{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}{3000\times {{10}^{-10}}}\]                 \[=6.6\times {{10}^{-19}}J\]                 \[=0.6\times {{10}^{-18}}J\] \[\therefore \]  \[{{W}_{0}}=e{{V}^{0}}=0.6\times {{10}^{-18}}J\] \[\therefore \]  \[{{V}^{0}}=\frac{0.6\times {{10}^{-18}}}{e}\]                 \[=\frac{0.6\times {{10}^{-18}}}{1.6\times {{10}^{-19}}}=3.75\,\,V\]


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