Question 188 of 191

A beam of unpolarised light of intensity ${I}_{0}$ is passed through a polaroid $A$ and then through another polaroid $B$ which is oriented so that its principle plane makes an angle of ${\text{45}}^{\text{o}}$ relative to that of $A$. The intensity of the emergent light is:

A$\dfrac{{I}_{0}}{4}$B$\dfrac{{I}_{0}}{8}$C${I}_{0}$D$\dfrac{{I}_{0}}{2}$

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Answer: (A) $\dfrac{{I}_{0}}{4}$

Relation between intensities is



${\text{I}}_{\text{R}}=\left(\dfrac{{\text{I}}_{0}}{2}\right){\text{cos}}^{2}\left({\text{45}}^{\text{o}}\right)=\dfrac{{\text{I}}_{0}}{2}\times \dfrac{1}{2}=\dfrac{{\text{I}}_{0}}{4}$