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CET Karnataka Medical CET - Karnataka Medical Solved Paper-2010

  • question_answer
    Red light of wavelength 625 nm is incident normally on an optical diffraction grating with\[{{S}_{2}}\]lines/m. Including central principal maxima, how many maxima may be observed on a screen which is far from the grating?

    A)  15              

    B)  17

    C)  8               

    D)  16

    Correct Answer: B

    Solution :

    For principal maxima in grating spectra\[\frac{\sin \theta }{N}=n\lambda \]where, n = (1, 2, 3) is the order of principal maxima and\[\theta \]is the angle of diffraction. \[n=\frac{1}{\lambda N}=\frac{1}{6.25\times {{10}^{-7}}\times 2\times {{10}^{5}}}=8\] \[\therefore \]Number of maxima\[=2n+1=2\times 8+1=17\]


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