10th Class Science Sources of Energy Question Bank Sources of Energy

  • question_answer
    The work function of a metal is 2.5 eV. If tin radiation of wavelength 4000A falls on it, then energy of emitted photoelectrons will be

    A)  0.402 eV

    B)  0.204 eV

    C)  0.306 eV

    D)  \[0.\text{6}0\text{3 eV}\]  

    Correct Answer: D

    Solution :

                    \[E=hv=\frac{hc}{\lambda }\]                 \[=\frac{6\cdot 63\times {{10}^{-34}}\times 3\times {{10}^{8}}}{4000\times {{10}^{-10}}}\]                 \[=4\times 966\times {{10}^{-19}}J\]                 \[=\frac{4\cdot 966\times {{10}^{-19}}}{1\cdot 6\times {{10}^{-19}}}eV=3\cdot 103\,\,eV\] Energy of emitted photon\[=(3.103-2.5)eV\]                 \[\mathbf{=0}\mathbf{.603}\,\,\mathbf{eV}\]


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