JEE Main & Advanced Physics Photo Electric Effect, X- Rays & Matter Waves Question Bank Self Evaluation Test - Dual Nature of Radiation and Matter

  • question_answer
    In the photoelectric experiment, if we use a monochromatic light, the I-V curve is as shown. If work function of the metal is 2eV, estimate the power of light used. (Assume efficiency of photo emission \[{{10}^{-3}}%\], i.e., number of photoelectrons emitted are \[{{10}^{-3}}%\]of number of photons incident on metal)      

    A) 2W

    B) 5W

    C) 7W

    D) 10W

    Correct Answer: C

    Solution :

    [c] The energy of incident photons is given by \[hv=e{{V}_{s}}+{{\phi }_{0}}=2+5=7eV\] (\[{{V}_{s}}\] is stopping potential and \[{{\phi }_{0}}\] is work function) Saturation current\[={{10}^{-5}}A\] \[=\frac{\eta P}{hv}e=\frac{{{10}^{-5}}P}{7\times e}e\] (\[\eta \] is photon emission efficiency) \[\therefore P=7W\]


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