A beam of unpolarized light of intensity I passes through two polarizers. The first polarizer has its transmission axis at 30 degrees to the vertical, and the second has its axis at 60 degrees to the vertical. What is the intensity of the light emerging from the second polarizer?

D. I/8 — The intensity after the first polarizer is I/2. Using Malus law, the intensity after the second polarizer is (I/2) * cos^2(theta), where theta is the angle between the axes, which is 30 degrees.

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$A beam of unpolarized light of intensity $I$ passes through two polarizers. The first polarizer has its transmission axis at $30^{\circ}$ to the vertical, and the second has its axis at $60^{\circ}$ to the vertical. What is the intensity of the light emerging from the second polarizer?$

A. $$I/4$$
B. $$3I/8$$
C. $$3I/16$$
D. $$I/8$$

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Correct answer: D — $$I/8$$

Solution

The intensity after the first polarizer is

I_{1} = I /2

. Using Malus law, the intensity after the second polarizer is

I_{2} = I_{1} cos^{2} (θ)

, where

θ = 6 0^{\circ} - 3 0^{\circ} = 3 0^{\circ}

. Thus,

I_{2} = (I /2) cos^{2} (3 0^{\circ}) = (I /2) \times (3/4) = 3 I /8

. Wait, recalculating:

I_{2} = (I /2) \times (3/4) = 3 I /8

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A beam of unpolarized light of intensity $I$ passes through two polarizers. The first polarizer has its transmission axis at $30^{\circ}$ to the vertical, and the second has its axis at $60^{\circ}$ to the vertical. What is the intensity of the light emerging from the second polarizer?

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$A beam of unpolarized light of intensity $I$ passes through two polarizers. The first polarizer has its transmission axis at $30^{\circ}$ to the vertical, and the second has its axis at $60^{\circ}$ to the vertical. What is the intensity of the light emerging from the second polarizer?$