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

  • question_answer
    Young's double slit experiment is made in a liquid. The \[{{10}^{th}}\] bright fringe lies in liquid where \[{{6}^{th}}\] dark fringe lies in vacuum. The refractive index of the liquid is approximately     

    A) 1.8   

    B) 1.5   

    C) 1.3 

    D) 1.6

    Correct Answer: A

    Solution :

    [a] Fringe width \[\omega =\frac{\lambda D}{d}\] When the apparatus is immersed in a liquid, then \[\lambda \] will decrease \[\mu \]times and hence\[\omega \]is reduced \[\mu \] (refractive index) times. \[10\omega '=(5.5)\omega \] or \[10\lambda '\left( \frac{D}{d} \right)=(5.5)\frac{\lambda D}{d}\] or \[\frac{\lambda }{\lambda '}=\frac{10}{5.5}=\mu \] or \[\mu =1.8\]


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