Unpolarized light is passed through polarizer 1.The light then goes though polarizer 2 with its plane of polarization at 44.0° to that of polarizer 1.What fraction of the intensity of the original light gets though the second polarizer?
A)0.360
B)0.518
C)0.259
D)0.720
E)0.500

Question

Quizplus · Accepted Answer

When unpolarized light passes through the first polarizer, only half of its intensity gets through, as the other half is absorbed. Therefore, the intensity of the light that reaches the second polarizer is 1/2 of the original intensity. 
When the light passes through the second polarizer, the intensity that makes it through is given by:
I_final = I_initial * cos^2(theta),
where theta is the angle between the planes of polarization of the two polarizers. 
Plugging in the values, we get:
I_final = (1/2) * cos^2(44.0°) = 0.259 * I_initial. 
Therefore, the fraction of the intensity of the original light that gets through the second polarizer is 0.259 or about 0.260, which is closest to choice C.

Unpolarized Light Is Passed Through Polarizer 1