JEE Main & Advanced Sample Paper JEE Main Sample Paper-23

  • question_answer
    In double slit interference experiment, the fringe width obtained with a light of wavelength \[5900\overset{0}{\mathop{A}}\,\] was \[1.2\] mm for parallel narrow slits placed 2 mm apart. In this arrangement, if the slit separation is increased by one - and - half times the previous value, then the fringe width is :

    A)  \[0.9\] mm                               

    B)  \[0.8\] mm

    C)  \[1.8\] mm                               

    D)  \[1.6\] mm

    Correct Answer: B

    Solution :

    Young's double slit interference experiment,\[b=\frac{\lambda D}{d}\] Given \[{{\beta }_{1}}=1.2\ mm\]\[\frac{{{d}_{2}}}{{{d}_{1}}}=1\,\frac{1}{2}\,=1.5\] So, \[\beta \propto \,\frac{1}{d}\Rightarrow \,\frac{{{\beta }_{1}}}{{{\beta }_{2}}}\,=\frac{1/{{d}_{1}}}{1/{{d}_{2}}}\Rightarrow \,\frac{{{\beta }_{1}}}{{{\beta }_{2}}}\,=\frac{{{d}_{1}}}{{{d}_{2}}}=1.5\] \[\Rightarrow \,\frac{1.2}{{{\beta }_{2}}}\,=1.5\Rightarrow \,{{\beta }_{2}}=\frac{1.2}{1.5}=\frac{4}{5}=0.8mm\]


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