Question

A polarizer - analyser set is adjusted such that the intensity of light coming out of the analyser is just 10% of the original intensity. Assuming that the polarizer - analyser set does not absorb any light, the angle by which the analyser need to be rotated further to reduce the output intensity to be zero, is ______.

Options

• 71.6°

• 18.4°

• 90°

• 45°

Answer 1

A polarizer - analyser set is adjusted such that the intensity of light coming out of the analyser is just 10% of the original intensity. Assuming that the polarizer - analyser set does not absorb any light, the angle by which the analyser need to be rotated further to reduce the output intensity to be zero, is 18.4°.

Explanation:

According to the enquiry, the intensity of light leaving the analyser is only a 100% of its initial intensity (I₀)

Using, I = I₀cos²θ

⇒ `"I"_0/10="I"_0cos^2theta`

⇒ `1/10=cos^2theta`

⇒ `cos theta=1/sqrt10=0.316`

⇒ θ ≈ 71.6°

In order to reduce the output intensity to zero, the analyzer must be rotated a further angle.

Φ = 90°- θ = 90°- 71.6° = 18.4°