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

  • question_answer
    Find the number of photon emitted per second by a 25 watt source of monochromatic light of wavelength \[\text{6600 }\overset{\text{o}}{\mathop{\text{A}}}\,\text{.}\]  What is the photoelectric current assuming 3% efficiency for photoelectric effect?

    A) \[\frac{25}{3}\times {{10}^{19}}J,0.4amp\]

    B) \[\frac{25}{4}\times {{10}^{19}}J,6.2amp\]

    C) \[\frac{25}{2}\times {{10}^{19}}J,6.2amp\]

    D) None of these

    Correct Answer: A

    Solution :

    [a] \[{{P}_{in}}=25W,\lambda =6000\overset{\text{o}}{\mathop{\text{A}}}\,=6000\times {{10}^{-10}}m\] \[nhv=P\] \[\Rightarrow \] Number of photons emitted/sec, \[n=\frac{P}{\frac{hc}{\lambda }}=\frac{P\lambda }{hc}=\frac{25\times 6600\times {{10}^{-10}}}{6.64\times {{10}^{-34}}\times 3\times {{10}^{8}}}\] \[=8.28\times {{10}^{19}}=\frac{25}{3}\times {{10}^{19}}\] 3% of emitted photons are producing current \[\therefore I=\frac{3}{100}\times ne=\frac{3}{100}\times \frac{25}{3}\times {{10}^{19}}\times 1.6\times {{10}^{-19}}\] \[=0.4A\]


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