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NEET NEET SOLVED PAPER 2013

  • question_answer
    In Young's double slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelengths \[{{\lambda }_{1}}=12000\overset{\text{o}}{\mathop{\,\text{A}}}\,\] and \[{{\lambda }_{2}}=10000\overset{\text{o}}{\mathop{\,\text{A}}}\,\]. At what minimum distance from the common central bright fringe on the screen 2 m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other?

    A) 8 mm           

    B) 6 mm

    C) 4 mm           

    D) 3 mm

    Correct Answer: B

    Solution :

    Given\[{{\lambda }_{1}}=12000{\AA}\] and \[{{\lambda }_{2}}=10000{\AA},\] \[D=2cm\]and\[d=2\,mm=2\times {{10}^{-3}}cm.\] We have\[\frac{{{\lambda }_{1}}}{{{\lambda }_{2}}}=\frac{{{h}_{1}}}{{{h}_{2}}}\] \[=\frac{12000}{10000}=\frac{6}{5}\] as \[x=\frac{{{u}_{1}}{{\lambda }_{1}}D}{d}=\frac{5\times 12000\times {{10}^{-10}}\times 2}{2\times {{10}^{-3}}}\] \[=5\times 1.2\times {{10}^{4}}\times {{10}^{-10}}\times {{10}^{3}}=6mm\]


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