Three polarizing filters are stacked with the polarizing axi

Three polarizing filters are stacked, with the polarizing axis of the second and third filters at angles of 28.8 and 64.4 , respectively, to that of the first. If unpolarized light is incident on the stack, the light has an intensity of 77.5 W/cm2 after it passes through the stack.

If the incident intensity is kept constant, what is the intensity of the light after it has passed through the stack if the second polarizer is removed?

Solution

I₃ = I₀ / 2 * cos² theta₂ * cos² (theta₃ - theta₂) = 77.5

77.5 = I₀ / 2 * cos² 28.8 * cos² (64.4 - 28.8)

I₀ = 305.74

I₃\' = I₀ / 2 * cos² theta₃

= 305.74  / 2 * cos² 64.4

= 28.53 W/cm²