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JEE Main & Advanced Sample Paper JEE Main - Mock Test - 25

  • question_answer
    In a two-slit experiment, with monochromatic light, fringes are obtained on a screen placed at some distance from the slits. If the screen is moved by \[5\times {{10}^{-2}}m\]towards the slits, the change in fringe width is \[{{10}^{-3}}m\]. Then the wavelength of light used is (given that distance between the slits is\[0.03\text{ }mm\])

    A) \[4000\text{ }\overset{o}{\mathop{A}}\,\]               

    B)       \[4500\text{ }\overset{o}{\mathop{A}}\,\]              

    C)   \[5000\text{ }\overset{o}{\mathop{A}}\,\]              

    D)        \[6000\text{ }\overset{o}{\mathop{A}}\,\]

    Correct Answer: D

    Solution :

    [d] \[\beta =\frac{\Delta \lambda }{d}\,\,\,\,\,\,\,\,:\,\,\,\,\,\,\,\,\,\,\Delta \beta =\frac{\lambda }{d}\Delta D\] \[{{10}^{-3}}=\frac{\lambda \times 5\times {{10}^{-2}}}{0.03\times {{10}^{-3}}}\] \[\lambda =\frac{0.03}{5}\times {{10}^{-6+2}}\,;\,\,\,\,\lambda =6000\overset{o}{\mathop{A}}\,\]


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