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JEE Main & Advanced Sample Paper JEE Main Sample Paper-33

  • question_answer
    In Young's experiment the source is red light of wave length \[7\times {{10}^{-7}}m\]. When a thin glass plate of refractive index 1.5 at this wavelength is put in the path of one of the interfering beams, the central bright shifts by \[{{10}^{-3\text{ }}}m\] to the position previously occupied by the 5th bright fringe then the thickness of the plate is :

    A)  \[4\mu m\]       

    B)                                     \[5\mu m\]

    C)  \[7\mu m\]     

    D)                                     \[9\mu m\]

    Correct Answer: C

    Solution :

    Shift \[=(\mu -1)\,t\,\frac{D}{d}\,=5\beta =5\frac{d\lambda }{d}\]             \[t=\frac{5\lambda }{(\mu -1)}\,=\frac{5\times 7\times {{10}^{-7}}}{(1.5-1)}\,=7\times {{10}^{-6}}=7\,\mu m\]


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