JEE Main & Advanced Physics Photo Electric Effect, X- Rays & Matter Waves Question Bank Topic Test - Photo Electric Effect, X-Rays & Matter Waves

  • 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             \[(h=6.6\times {{10}^{-34}}Js,\ \ e=1.6\times {{10}^{-19}}C,\ \ c=3\times {{10}^{8}}m{{s}^{-1}})\]

    A) 1.1

    B) 2.0

    C) 2.2

    D) 3.1

    Correct Answer: A

    Solution :

    [a] 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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