CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2007

  • question_answer
    If the polarizing angle of a piece of glass for green light is\[54.74{}^\circ ,\]then the angle of minimum deviation for an equilateral prism made of same glass is [Given: \[tan\text{ }54.74{}^\circ =1.414\]]

    A)  \[45{}^\circ \]                                  

    B)  \[54.74{}^\circ \]                            

    C)  \[60{}^\circ \]                  

    D)         \[90{}^\circ \]

    E)  \[30{}^\circ \]

    Correct Answer: E

    Solution :

    By Brewsters law, \[\mu =\tan {{\theta }_{p}}\] or        \[\mu =\tan 54.74{}^\circ \] or         \[\mu =1.414\] For an equilateral prism, \[\angle A=60{}^\circ \] \[\therefore \]  \[\mu =\frac{\sin \left( \frac{A+{{\delta }_{m}}}{2} \right)}{\sin \left( \frac{A}{2} \right)}\] Or           \[1.414=\frac{\sin \left( \frac{60{}^\circ +{{\delta }_{m}}}{2} \right)}{\sin \left( \frac{60{}^\circ }{2} \right)}\] Or           \[\frac{1.414\times 1}{2}=\sin \left( \frac{60{}^\circ +{{\delta }_{m}}}{2} \right)\]                                                 \[[\because 1.414=\sqrt{2}]\] Or           \[\frac{\sqrt{2}}{2}=\sin \left( \frac{60{}^\circ +{{\delta }_{m}}}{2} \right)\] Or           \[\frac{1}{\sqrt{2}}=\sin \left( \frac{60{}^\circ +{{\delta }_{m}}}{2} \right)\] Or           \[45{}^\circ =\left( \frac{60{}^\circ +{{\delta }_{m}}}{2} \right)\] Or           \[\delta =30{}^\circ \]


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