Question

Two polarizers are oriented at 35?° to each other and plane-polarized light is incident on them. If only 35% of the light gets through both of them, what was the initial polarization direction of the incident light? Find the angle between the initial polarization direction of the incident light and the axis of first polarizer.

Answer 1

Let the initial polarization direction of the incident light be x degree with respect to vertical which is assmed the axis of first polarizer.

After first polarizer intensity decreases to cos² x of initial.

After second polarizer intensity decreases to : cos² x * cos²35 of initial

Now,  cos² x * cos²35 = 0.35   

so x = 43.76 degree,

The initial polarization direction of the incident light = 43.76 degree to the left or anticlockwise of vertical axis.

Thus the angle between the initial polarization direction of the incident light and the axis of first polarizer = 43.76 degree.