The figure below shows four polarizers with the first at the

The figure below shows four polarizers with the first at theta_A = 0, the second at theta_B = 30 degree, the third at theta_C = 60 degree, and the fourth at theta_D = 90 degree. Unpolarized light with intensity, I_0, is incident on polarizer A from the left. What is the intensity of the light, I_4, after it passes through all four polarizers? One of the polarizers is removed. If the intensity of light through the remaining three is increased, which ones could have been removed? (There is more than one answer.)

Solution

Intensity of the unpolarized light = Io

Intensity of the light after passing through A is I = Io/2 = 0.5 Io

Intensity of the light after passing through B is I \" = I \' cos ² 30

                                                                       = 0.5 Io (0.75)

                                                                       = 0.375 Io

Intensity of the light after passing through C is I \'\" = I \'\' cos ² (60-30)

                                                                       = 0.375 Io (0.75)

                                                                       = 0.28125 Io

Intensity of the light after passing through D is I \"\" = I \"\' cos ² (90-30)

                                                                       = 0.28125 Io (0.75)

                                                                       = 0.2109 Io

(b). Answers are A

                         D