What causes the intensity to vary when a second polaroid is rotated in front of another polaroid through which unpolariz
**Convex lens focusing** plane wave into point because lens introduces phase delay proportional to thickness, converting plane wavefront to spherical converging to focal point, property ensures rays parallel to axis meet at focus, spherical aberration minimized for paraxial rays, lensmaker's formula determines focal length. The first polaroid polarizes the light linearly, and the second allows only the component of the electric field aligned with its pass-axis, varying with the angle via Malus’ law. Using Δ = d sinθ, y = n λ D/d, a sinθ = n λ, I = I₀ cos²θ, n = c/v, sinC = 1/n, λ' = λ/n and A
Ref: NCERT > Physics Book > Wave Optics > Optical Phenomena and Applications