A plane polarised light is incident on a polariser with its pass axis making angle θ with x-axis, as shown in the figure. At four different values of θ, θ=8°, 38°, 188° and 218°, the observed intensities are same. What is the angle between the direction of polarisation and x-axis?

Question

Accepted Answer

(1) 203°. I∝cos²(θ-φ), where φ is the polarisation direction; it repeats every 180°. Equal intensity at 8° and 38° means φ is midway, 23° (or 23°+90°). The pair 188°, 218° gives the same result shifted by 180°: φ=203° is equivalent to 23°. Among the options, 203° fits.

A plane polarised light is incident on a polariser with its pass axis making angle θ with x-axis, as shown in the figure. At four different values of θ, θ=8°, 38°, 188° and 218°, the observed intensities are same. What is the angle between the direction of polarisation and x-axis?

Step-by-step solution

Why the other options are wrong