Question

The intensity of a polarized light can be controlled by a second polarizer from

• A. 100\% to 0\%
• B. 50\% to 0\%
• C. 25\% to 0\%
• D. 10\% to 0\%
• E. 75\% to 0\%

Hint:

Unpolarized light becomes partially polarized after the first polarizer, reducing its intensity by half. A second polarizer can then control this intensity from 50\% to 0\%, based on their relative orientation.

Answer 1

The Correct Option is B

The intensity of polarized light passing through a second polarizer is governed by Malus's Law, which states: \[ I = I_0 \cos^2 \theta \] where: - I is the intensity of light after passing through the second polarizer,
- I_0 is the initial intensity of the polarized light,
- \theta is the angle between the polarization direction of the first polarizer and the transmission axis of the second polarizer.
When unpolarized light passes through the first polarizer, its intensity is reduced to 50\% because only one plane of polarization is allowed to pass.
After that, using a second polarizer (also called an analyzer), the intensity can be further varied depending on the angle \theta . The maximum intensity occurs when \theta = 0^\circ ( \cos^2 0^\circ = 1 ), so output is 50\% of original. The minimum intensity occurs when \theta = 90^\circ ( \cos^2 90^\circ = 0 ), so output is 0\%. Therefore, the intensity of polarized light can be controlled from 50\% to 0\% by rotating the second polarizer. Hence, the correct answer is (B) 50\% to 0\% .