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CET Karnataka Medical CET - Karnataka Medical Solved Paper-2010

  • question_answer
    What is the minimum thickness of a thin film required for constructive interference in the reflected light from it? Given, the refractive index of the film = 1.5, wavelength of the light incident on the film = 600 nm.

    A)  100 nm       

    B)  300 nm

    C)  50 nm        

    D)  200 nm

    Correct Answer: A

    Solution :

    Condition for constructive interference is \[2\mu t=[2n+1]\frac{\lambda }{2}\] where,         n= 0,1, 2,3... For minimum thickness, n = 0 \[2\mu t=\frac{\lambda }{2}\] \[\Rightarrow \] \[t=\frac{\lambda }{4\mu }=\frac{600\times {{10}^{-9}}}{4\times 1.5}\]\[=100nm\]


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