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JEE Main & Advanced JEE Main Paper (Held on 12-4-2019 Afternoon)

  • question_answer
              A system of three polarizers \[{{P}_{1}},{{P}_{2}},{{P}_{3}}\]is set up such that the pass axis of\[{{P}_{3}}\]is crossed with respect to that of \[{{P}_{1}}\]. The pass axis of \[{{P}_{2}}\]is inclined at \[60{}^\text{o}\] to the pass axis of \[{{P}_{3}}\]. When a beam of unpolarized light of intensity \[{{I}_{0}}\] is incident on \[{{P}_{1}},\]the intensity of light transmitted by the three polarizers is I. The ratio \[({{I}_{0}}/I)\] equals (nearly) : [JEE Main 12-4-2019 Afternoon]

    A) 16.00              

    B) 1.80

    C) 5.33                

    D) 10.67

    Correct Answer: D

    Solution :

    Since unpolarised light falls on \[{{P}_{1}}\Rightarrow \] intensity of light transmitted from \[{{P}_{1}}=\frac{{{I}_{0}}}{2}\] Pass axis of \[{{P}_{2}}\]will be at an angle of \[30{}^\text{o}\] with\[{{P}_{1}}\] \[\therefore \]Intensity of light transmitted from \[{{P}_{2}}=\frac{{{I}_{0}}}{2}{{\cos }^{2}}{{30}^{o}}=\frac{3{{I}_{0}}}{8}\] Pass axis of \[{{P}_{3}}\]is at an angle of \[60{}^\text{o}\] with \[{{P}_{2}}\] \[\therefore \]Intensity of light transmitted from \[{{P}_{3}}=\frac{3{{I}_{0}}}{8}{{\cos }^{2}}{{60}^{o}}=\frac{3{{I}_{0}}}{32}\] \[\therefore \]\[\left( \frac{{{I}_{0}}}{I} \right)=\frac{32}{3}=10.67\]


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