Question

Two polaroids are placed with their optic axis perpendicular to each other. One of them is rotated through 45, what is the intensity of light emerging from the second polaroid if i0 is the intensity of unpolarised light?

Answer 1

The intensity of light emerging from the second polaroid is :

• If i0 is the intensity of unpolarised light

• Two polaroids are placed with their optic axis perpendicular to each other.

• One of them is rotated through 45°

• Intensity through first Polaroid would be i0/2

Then applying malus law that states " The intensity of plane-polarized light that passes through an analyzer varies as the square of the cosine of the angle between the plane of the polarizer and the transmission axes of the analyzer. "

• Formula : I = Io cos^2 ϕ

I = i0×cos^2(45°) = i0/2×(1/√2)^2

= i0/4

Hence, the intensity of light emerging from the second polaroid is i0/4