JEE Main & Advanced Physics Photo Electric Effect, X- Rays & Matter Waves Question Bank Photon and Photoelectric Effect

  • question_answer
    The work function of metal is 1 eV. Light of wavelength 3000 Å is incident on this metal surface. The velocity of emitted photo-electrons will be                       [MP PMT 1990]

    A)            10 m/sec                                

    B)            \[1\times {{10}^{3}}\]m/sec

    C)            \[1\times {{10}^{4}}m/\sec \]m/sec                              

    D)            \[1\times {{10}^{6}}m/\sec \]m/sec

    Correct Answer: D

    Solution :

                       \[E={{W}_{0}}+{{K}_{\max }};\ E=\frac{12375}{3000}=4.125\ eV\]                    \[\Rightarrow {{K}_{\max }}=E-{{W}_{0}}=4.125\ eV-1\ eV=3.125\ eV\]                    \[\Rightarrow \frac{1}{2}mv_{\max }^{2}=3.125\times 1.6\times {{10}^{-19}}\ J\]            \[\Rightarrow {{v}_{\max }}=\sqrt{\frac{2\times 3.125\times 1.6\times {{10}^{-19}}}{9.1\times {{10}^{-31}}}}\]\[=1\times {{10}^{6}}m/s\]


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