Practice question

**Polarization** transverse wave property, light after polaroid polarized along pass-axis, Malus law I = I₀ cos²θ, θ angle between pass-axes, initial unpolarized intensity I₀ after first polaroid I₁ = I₀/2, after second at 45° I₂ = I₁ cos²45°= I₀/2×0.5= I₀/4, after two perpendicular 90° I=0 because cos90°=0, for 60° I= I₀/2×cos²60°= I₀/2×0.25= I₀/8. For unpolarized light, intensity after one polaroid is (I₀/2) . Rotating by 90° from the pass-axis gives I = (I₀/2) cos² 90° = 0 . It reduces to zero from its initial value. Using Δ = d sinθ, y = n λ D/d, a sinθ = n λ, I = I₀ cos²θ,