NEET Sample Paper NEET Sample Test Paper-21

  • question_answer The human eye can barely detect yellow light (6000 A) that delivers\[1.7\times {{10}^{-18}}\]watt to the retina. Nearly how many photons per second does the retina receive?

    A)  50                 

    B)  5

    C)  500                

    D)  More than 5 million

    Correct Answer: B

    Solution :

    Let n be the number of photons falling per second on the retina, then, \[nhv\] \[=1.7\times {{10}^{-18}}\] or \[\frac{nhc}{\lambda }=1.7\times {{10}^{-18}},\]or \[n=\frac{1.7\times {{10}^{-18}}\lambda }{hc}\] \[\therefore \]\[n=\frac{1.7\times {{10}^{-18}}\times 6000\times {{10}^{10}}}{6.6\times {{10}^{-34}}\times 3\times {{10}^{-8}}}=5.15=5.\] Hence, the correction option is (b).

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