Question

The following items are positioned in sequence: A source of a beam of natural light of intensity lo, three ideal polarizers A, B, and C; and an observer. Polarizer axis angles are measured clockwise from the vertical, as viewed by the observer. The axis angle of polarizer A is set at 0° (vertical), and the axis angle of polarizer C is set at 50°. Polarizer B is set so that the beam intensity at the observer is a maximum. What is the axis angle settings of polarizer B?​

Answer 1

θ₁ = 140º, θ₂ = -40º

Explanation:

For this exercise we must use Malus’s law

I = Io cos² θ

where the angle is between two polarizers.

When the non-polarized light reaches the first polarized light, the vertically polarized light passes

I₁ = I₀ / 2

This light reaches the second polarizer and the light that comes out of this polarizer must reach the third polarized one, it is requested that no light comes out of it, for which the polarizer B must be at 90º from the third, so the possible angles are

θ₁ = 50 + 90 = 140º

θ₂ = 50 – 90 = -40º

Answer 2

θ₁ = 140º, θ₂ = -40º

Explanation:

For this exercise we must use Malus’s law

I = Io cos² θ

where the angle is between two polarizers.

When the non-polarized light reaches the first polarized light, the vertically polarized light passes

I₁ = I₀ / 2

This light reaches the second polarizer and the light that comes out of this polarizer must reach the third polarized one, it is requested that no light comes out of it, for which the polarizer B must be at 90º from the third, so the possible angles are

θ₁ = 50 + 90 = 140º

θ₂ = 50 – 90 = -40º