Chhattisgarh PMT Chhattisgarh PMT Solved Paper-2007

  • question_answer
    In two separate set-ups of the Young's double slit experiment fringes of equal width are observed when lights of wavelengths in the ratio 1:2 are- used. If the ratio of the slit separation in the two cases is 2:1 the ratio of the distance between the plane of the slits and the screen in the two set-ups is

    A)  4:1                                        

    B)  1:1

    C)  1:4                                        

    D)  2:1

    Correct Answer: A

    Solution :

    Given,  \[\frac{{{\lambda }_{1}}}{{{\lambda }_{2}}}=\frac{1}{2},\]\[\frac{{{d}_{1}}}{{{d}_{2}}}=\frac{2}{1}\] Fringe width in interference is given by,                 \[\beta =\frac{D\lambda }{d}\] Given    \[{{\beta }_{1}}={{\beta }_{2}}\]                 \[\frac{{{D}_{1}}{{\lambda }_{1}}}{{{d}_{1}}}=\frac{{{D}_{2}}{{\lambda }_{2}}}{{{d}_{2}}}\]                 \[\frac{{{D}_{1}}}{{{D}_{2}}}=\frac{{{d}_{1}}}{{{d}_{2}}}\times \frac{{{\lambda }_{2}}}{{{\lambda }_{1}}}=\frac{2}{1}\times \frac{2}{1}=\frac{4}{1}\]


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