Optics 6 Question 15
17. 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 principal plane makes an angle of $45^{\circ}$ relative to that of $A$. The intensity of the emergent light is
(a) $I _0$
(b) $I _0 / 2$
(c) $I _0 / 4$
(d) $I _0 / 8$
(2013 Main)
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Solution:
- Relation between intensities is
$$ I _R=\frac{I _0}{2} \cos ^{2}\left(45^{\circ}\right)=\frac{I _0}{2} \times \frac{1}{2}=\frac{I _0}{4} $$
