JEE Main & Advanced Physics Wave Optics / तरंग प्रकाशिकी Question Bank Self Evaluation Test - Wave Optics

  • question_answer
    Interference fringes were produced using white light in a double slit arrangement. When a mica sheet of uniform thickness of refractive index 1.6 (relative to air) is placed in the path of light from one of the slits, the central fringe moves through some a distance. This distance is equal to the width of 30 interference bands if light of wavelength is used. The thickness \[(in\,\,\mu m)\] of mica is

    A) 90   

    B) 12   

    C) 14   

    D) 24

    Correct Answer: D

    Solution :

    [d] Shift of fringe pattern \[=(\mu -1)\frac{tD}{d}\] \[\therefore \,\,\,\frac{30D(4800\times {{10}^{-10}})}{d}=(0.6)t\frac{D}{d}\] \[30\times 4800\times {{10}^{-10}}=0.6t\] \[t=\frac{30\times 4800\times {{10}^{-10}}}{0.6}=\frac{1.44\times {{10}^{-5}}}{0.6}=24\times {{10}^{-6}}\]


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