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

  • question_answer
    Light of wavelength 4000 Å falls on a photosensitive metal and a negative 2V potential stops the emitted electrons. The work function of the material (in eV) is approximately            \[(h=6.6\times {{10}^{-34}}Js,\ \ e=1.6\times {{10}^{-19}}C,\ \ c=3\times {{10}^{8}}m{{s}^{-1}})\]  [MP PMT 1995; MH CET 2004]

    A)            1.1 

    B)            2.0

    C)            2.2 

    D)            3.1

    Correct Answer: A

    Solution :

                       Energy of incident light \[E\,(eV)=\frac{12375}{4000}=3.09\,eV\] Stopping potential is ? 2V  so \[{{K}_{\max }}=2\,eV\] Hence by using \[E={{W}_{0}}+{{K}_{\max }}\]; W0\[=1.09\,eV\]\[\approx \,1.1\,eV\]


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