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NEET Sample Paper NEET Sample Test Paper-89

  • question_answer
    In Young's expt., the distance between two slits is \[\frac{d}{3}\] and the distance between the screen and the slit is 3 D. The number of fringes in \[\frac{1}{3}m\] on the screen, formed by monochromatic light of wavelength \[3\lambda ,\] will be

    A) \[\frac{d}{9D\lambda }\]

    B)        \[\frac{d}{27D\lambda }\]

    C) \[\frac{d}{81\,\,D\lambda }\]      

    D)        \[\frac{d}{D\lambda }\]

    Correct Answer: C

    Solution :

    [c] \[\beta =\frac{\lambda 'D'}{d'}=\frac{3\lambda \,3D}{d/3}=27\frac{\lambda D}{d}.\] No. of fringes \[=\frac{1/3}{\beta }=\frac{d}{81\lambda \,\,D}.\]


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