Two polarised sheets are placed one over the other with their axes inclined to each other at 60°. The ratio of the intensity of unpolarised incident light and polarised emergent light is:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 8 : 1
Unpolarised light of intensity \( I_0 \) passing through the first sheet comes out plane polarised with half the intensity, \( I_1 = I_0/2 \). The second sheet transmits \( \cos^{2}\theta \) of this by Malus' law, where \( \theta \) is the angle between the two axes.
\( \displaystyle I_2 = I_1\cos^{2}60^\circ = \frac{I_0}{2}\times\frac{1}{4} = \frac{I_0}{8} \)
\( \displaystyle \frac{I_0}{I_2} = \frac{8}{1} \)