Unpolarized light is passed through polarizer 1.The light then goes though polarizer 2 with its plane of polarization at 39.8° to that of polarizer 1.Polarizer 3 is placed after polarizer 2.Polarizer 3 has its plane of polarization at 30.8° to the plane of polarization of polarizer 2 and at 70.6° to that of polarizer 1.What fraction of the intensity of the original light gets though the last polarizer?
A) 0.436
B) 0.664
C) 0.332
D) 0.218
E) 0.085

Question

Unpolarized light is passed through polarizer 1.The light then goes though polarizer 2 with its plane of polarization at 39.8° to that of polarizer 1.Polarizer 3 is placed after polarizer 2.Polarizer 3 has its plane of polarization at 30.8° to the plane of polarization of polarizer 2 and at 70.6° to that of polarizer 1.What fraction of the intensity of the original light gets though the last polarizer?
A) 0.436
B) 0.664
C) 0.332
D) 0.218
E) ​0.085

Quizplus · Accepted Answer

The intensity of light after passing through multiple polarizers is given by Malus's Law. After the first polarizer, the intensity is halved. After the second polarizer, the intensity is reduced by cos²(39.8°). After the third polarizer, the intensity is further reduced by cos²(30.8°). Calculating these gives approximately 0.218 of the original intensity.

Unpolarized Light Is Passed Through Polarizer 1