Power of a source of 2mW and wavelength 400nm light is directed on a photoelectric cell.If the current in the cell is 0.40 microampere,then the percentage of the incident photons that produce photoelectrons is 

Please solve this question and explain it.

Solution:P =2mW =2×10-3WEnergy of each photon =hcλ=6.62×10-34×3×1084×10-7=4.96×10-19JNumber of photons incident per second =PEnergy of each photon=2×10-34.96×10-19 4×1015 Let  n percentage of the incident photons that produce photoelectrons The number of photo electrons produced=n%×4×1015 Current i =n%×4×1015×1.6×10-190.40×10-6 =n%×4×1015×1.6×10-19n% =4×10-74×1015×1.6×10-19=0.625×10-3or n =0.06%
 

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