Unpolarised light of intensity 32 W m⁻² passes through three polaroids. The pass axis of the last polaroid is perpendicular to that of the first. If the emerging intensity is 3 W m⁻², find the angle between the pass axes of the first two polaroids. Image
Physics · Circular Motion
JEE Mains 10 April 2023 Shift 1 Morning Shift

Question

Unpolarised light of intensity 32 W m⁻² passes through three polaroids. The pass axis of the last polaroid is perpendicular to that of the first. If the emerging intensity is 3 W m⁻², find the angle between the pass axes of the first two polaroids. Image

Physics · Circular Motion

JEE Mains 10 April 2023 Shift 1 Morning Shift

G1 Physics · Accepted Answer

After the first polaroid, the intensity becomes I₁ = 32/2 = 16 W m⁻² Let the angle between the first and second polaroids be θ. The angle between the second and third is 90° − θ. By Malus' law, I = 16 cos²θ cos²(90° − θ) = 16 cos²θ sin²θ = 4 sin²2θ Given I = 3: 4 sin²2θ = 3 sin2θ = √3/2 Therefore, 2θ = 60° or 120° Hence, θ = 30° or 60° The source solution accepts both values.