1) You have a collection of three polarizers, and a source of unpolarized light

Question

1) You have a collection of three polarizers, and a source of unpolarized light of intensity lo. [Answers to some of the following questions could be in the form: "0.2%", etc.] a) Suppose, using all three polarizers, but the first and the third have an angle of 90 degrees between them How would you place the middle polarizer (at what angle) to now get the highest possible output intensity after the third polarizer? b) in case A above suppose the angle between the first two polarizers were 30 degrees (and first and third are perpendicular still)-what is the final intensity? c) Consider only the first two polarizers (leave out the third-you want to have 0.25% final intensity-what angle needs to be between the first and second polarizer?

Explanation / Answer

. a) As unpolarized light is incident on the polarizer the output intensity will be halved i.e 0.5 Io. Since the third polarizer is perpendicular to the first , for maximum intensity to pass through the second polarizer must be at an angle 450 with first.

b) The intensity after the first polarizer I 1 = 0.5 I o

Intensity after second polarizer I2 = I1cos245 = 0.5I1 = 0.25Io

The angle between second and third will ve 60o so the intensity of light after third will be

I3 = I2 cos245 = 0.5 I2 = 0.5 (0.25 Io) = 0.125 Io

c) I2 = I1 cos2x

I1 = 0.5 Io

I2 = 0.25Io

0.25 Io = 0.5Io cos2x

cos2x = 0.5

cosx = 0.25

x =45o

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