Question

Find the final intensity of light (\(I''\)), if the angle between the axes of two polaroids is \(60^\circ\). 

• A. \(\dfrac{3I_0}{2}\)
• B. \(\dfrac{I_0}{2}\)
• C. \(\dfrac{I_0}{4}\)
• D. \(\dfrac{I_0}{8}\)

Hint:

Unpolarised light loses half its intensity at the first polaroid.

Answer 1

The Correct Option is D

Step 1: After first polaroid: \[ I'=\frac{I_0}{2} \]
Step 2: After second polaroid (Malus law): \[ I''=I'\cos^2 60^\circ=\frac{I_0}{2}\times\frac{1}{4} \] \[ I''=\frac{I_0}{8} \]