JEE Main & Advanced Physics Wave Optics / तरंग प्रकाशिकी Question Bank Self Evaluation Test - Wave Optics

  • question_answer
    A light of wavelength \[6000\overset{o}{\mathop{A}}\,\] shines on two narrow slits separated by a distance 1.0 mm and illuminates a screen at a distance 1.5 m away. When one slit is covered by a thin glass plate of refractive index 1.8 and other slit by a thin glass plate of refractive index\[\mu \], the central maxima shifts by 0.1 rad. Both plates have the same thickness of 0.5 mm. The value of refractive index \[\mu \]of the glass is          

    A) 1.4 

    B) l5

    C) 1.6

    D) None of these

    Correct Answer: C

    Solution :

    [c] Change in path difference for any point on screen is \[|\mu -1.8|t.\] For central maxima, phase difference = 0. Hence, \[d\sin \theta -|\mu -1.8|t=0\] \[\Rightarrow \,\,\,d\,\theta =|\mu -1.8|t\] [q is very small and is in radian] \[\Rightarrow \,\,\left| \mu -\left. 1.8 \right| \right.=\frac{{{10}^{-3}}\times 0.1}{0.5\times {{10}^{-3}}}=0.2\Rightarrow \mu =2\] or 1.6


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