he figure below shows three wire - grid polarizers which consist of closely spac
ID: 1871907 • Letter: H
Question
he figure below shows three wire - grid polarizers which consist of closely spaced parallel thin conducting wires. The light that passes through this type of polarizer is observed to be linearly polarized at right angles to the wires.
(a) Explain the operation of wire - grid polarizers?
(b) Assuming that before the first polarizer the light was unpolarized with an intensity I0 = 2 x 10-6 W/m2, calculate the intensity after each polarizer. (Note: the angle between the polarization direction of each polarizer and the polarization direction of the previous polarizer is 45o).
Explanation / Answer
From Malus law
I = I0 cos ^2 theta
here the first polarizer is at an angle of theta = 90 degrees so the intensity is zero means not polarizerd
the second polarizer is at an angle of 45 degrees
I2 = I0 cos^2 theta
I2 = I0 cos^2(45)
I2 = I0/2 = 2*10^-6 = 1*10^-6 W/m^2
from the third polarizer the angle theta = 0 degrees
the intensity is I3 = I0 cos^2 theta
I3 = I0 cos^2(0)
I3 = I0 = 2*10^-6 W/m^2
which is linearly polarized
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