Question

PROBLEM #2: Max has two pairs of polarized sunglasses. Each of the four lenses has a polarization axis that is vertical (perpendicular to the ground) when worn. Max removes three of the lenses from the glasses and arranges them in front of the fourth lens so that the polarization axes of the first and the fourth lens are perpendicular to each other. He places the other two lenses between the outermost lenses, rotating the second and third lens so that the polarization axis of the second lens is tilted an angle of 0 with respect to that of the first lens, the third lens' polarizaiton axis is tilted 0 with respect to the second, and the fourth lens' axis is tilted by () with respect to the third. (a) Max holds the lens configuraiton in front of one eye and points it at the Sun. (Do not try this at home - or anywhere else, for that matter!!!) The intensity of the Sunlight entering the lenses is I.. What percentage of the light is blocked? (b) Max decides to remove one of the middle lenses without rotating any of the other lenses. What percentage of the incident light is transmitted by removing one of these lenses?

Answer 1

The sun light is randomly polarized. Hence the intensity of sunlight after passing through the After each polarizer the 2 first polarizer will he reduced to half of incident intensity, that is 0 cos e where Iis the intensity transmitted intensity follows the Malus law, I = I, of incident light on each of the polarizers Incidat ckdent Combination of 4 polarizers a. cos ecos cos e 2 Transmitted intensity I =- 1-0 으 cos" 6 Given that 30 =90° = 30° Then I cos 30 2 Percentage of blocked light Ikad x100 cos 30 2 -x100 = 78.9 % b. If one of the polarizers removed the relative angle between one pair of polarizers will become 60 Transmitted light I = ^cos 30 cos 60 2 = Percentage of blocked light Ial x 100 blockad -cos2 30 cos2 60 -x100 O =90.6%