Question

A polariser and an analyser are oriented so that maximum light is transmitted. What is the fraction of the maximum light transmitted when analyser is rutated through (i) 30° and (ii) 60°?

Answer 1

From Malus law, we have

I = I₀ cos² θ

(i) For θ = 30°

I = I₀ cos² 30° = I₀ \((\frac{\sqrt3}{2})^2 = \frac{3}{4}\) I₀

∴ \(\frac{I}{I_0} = \frac{3}{4}\) = 0.75

(ii) For θ = 60°

I = I₀ cos₂ 60° = I₀ \((\frac{1}{2})^2 = \frac{I_0}{4}\)

\(\frac{I}{I_0} = \frac{1}{4}\) = 0.25