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

  • question_answer
    A light wave of wavelength\[{{\lambda }_{0}}\]propagates from point A to point B. We introduce in its path a glass plate of refractive index n and thickness l. The introduction of the plate alters the phase of the plate at B by an angle\[\phi \]. If \[\lambda \] is the wavelength of lights on emerging from the plate, then

    A) \[\Delta \phi =0\]

    B)        \[\Delta \phi =\frac{2\pi l}{{{\lambda }_{0}}}\]

    C) \[\Delta \phi =2\pi {{\ln }^{2}}\left( \frac{1}{\lambda }-\frac{1}{{{\lambda }_{0}}} \right)\]

    D) \[\Delta \phi =\frac{2\pi l}{{{\lambda }_{0}}}(n-1)\]

    Correct Answer: D

    Solution :

    [d] \[{{\phi }_{i}}=\frac{2\pi }{{{\lambda }_{0}}}\ell \]  \[{{\phi }_{f}}=\frac{2\pi }{\lambda }\ell \] \[\Delta \phi =2\pi \ell \left( \frac{1}{\lambda }-\frac{1}{{{\lambda }_{0}}} \right)\] Further, by Snell's law \[n\lambda =(1){{\lambda }_{0}}\Rightarrow \lambda =\frac{{{\lambda }_{0}}}{n}\Rightarrow \Delta \phi =\frac{2\pi l}{{{\lambda }_{0}}}(n-1)\]


You need to login to perform this action.
You will be redirected in 3 sec spinner