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

  • question_answer
    In Young's double-slit experiment, the angular width of a fringe formed on a distant screen is \[1{}^\circ .\] The wavelength of light used is\[6000\,\,\overset{\text{o}}{\mathop{\text{A}}}\,\]. What is the spacing between the slits?

    A) 344 mm

    B) 0.1344 mm

    C) 0.0344 mm       

    D) 0.034 mm

    Correct Answer: C

    Solution :

    [c] In Young's double slit fringe with \[\sin \theta =\theta =y/D\] So, \[\Delta y/D\]and hence angular fringe width \[{{\theta }_{0}}=\Delta \theta \,(with\Delta y=\beta )\] Will be \[{{\theta }_{0}}=\frac{\beta }{D}=\frac{D\lambda }{d}\times \frac{1}{D}=\frac{\lambda }{d}\] \[\Rightarrow {{\theta }_{0}}={{1}^{0}}=\left( \frac{\pi }{180} \right)\]rad, and \[\lambda =6\times {{10}^{-7}}m\] Or \[d=\frac{\lambda }{{{\theta }_{0}}}=\frac{180}{\pi }\times (6\times {{10}^{-7}})=3.44\times {{10}^{-5}}m\] Or \[d=0.0344mm\]       


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