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

  • question_answer
    1.5 mW of 400 nm light is directed at a photoelectric cell. If 0.10 per cent of the incident photons produce photoelectrons, then find the current in the cell.        

    A) \[4.8\mu A\]

    B) \[48\mu A\]

    C) \[1.8\mu A\]

    D) \[0.48\mu A\]

    Correct Answer: D

    Solution :

    [d] The number of photons per second directed at the cell is \[n=\frac{\text{Power}}{hv}=\frac{P\lambda }{hc}=\frac{1.5\times {{10}^{-3}}\times 400\times {{10}^{-9}}}{6.62\times {{10}^{-34}}\times 3\times {{10}^{8}}}\] \[n=\frac{1}{3.31}\times {{10}^{16}}(\text{photons/s})\] But it is given that only 0.1 % of these photons produce photoelectrons. Therefore number of photoelectrons produced per second is \[{{n}_{e}}=\frac{0.1}{100}\times \frac{{{10}^{16}}}{3.31}=\frac{{{10}^{13}}}{3.31}\] Therefore, the current is \[I={{n}_{e}}e\] \[=\frac{{{10}^{13}}\times 1.6\times {{10}^{-19}}}{3.31}=0.48\times {{10}^{-6}}=0.48\mu A\]


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