Unpolarized light of intensity I_0 passes sequentially through two ideal polarizers whose transmission axes are oriented at an angle of 60 degrees to each other. What is the transmitted intensity?
Answer and explanation
Correct answer: C. I_0 / 8 (0.125 I_0)
- Step 1: After the first polarizer, Malus' law for unpolarized light states I_1 = I_0 / 2. Step 2. After the second polarizer at theta = 60°: I_2 = I_1 cos^2(60°). Step 3. cos(60°) = 1/2, so cos^2(60°) = 1/4. Step 4. I_2 = (I_0 / 2) (1/4) = I_0 / 8. Answer: I_0 / 8 (0.125 I_0). Why not the others: I_0 / 4 forgets that the first polarizer cuts unpolarized intensity by half.
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