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NEET Sample Paper NEET Sample Test Paper-88

  • question_answer
    A Laser light of wavelength 660 nm is used to weld Retina detachment. If a Laser pulse of width 60 ms and power 0.5 kW is used the approximate number of photons in the pulse are : [Take Planck's constant h \[=6.62\times {{10}^{-34}}Js\]]

    A) 1020    

    B)        1018   

    C) 1022                

    D)        1019

    Correct Answer: A

    Solution :

    [a] Given, \[\lambda =600\,nm,\] Power \[=0.5\,kW,\]t\[=60\,ms\] Power P \[=\frac{nhc}{\lambda t}\]\[\Rightarrow \]\[n=\frac{p\lambda t}{hc}\] \[=0.5\times {{10}^{3}}\times \frac{660\times {{10}^{-9}}\times 60\times {{10}^{-3}}}{6.6\times {{10}^{-34}}\times 3\times {{10}^{8}}}\] \[=100\times {{10}^{18}}={{10}^{20}}\]


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