Shine the light through two polarizing filters oriented at 90° to each other, so

Question

Shine the light through two polarizing filters oriented at 90° to each other, so that no light gets through. Now put a third polarizer in between them, at 45° to each of the existing filters, and observe whether light gets through. Try to figure out why it happens:

a) Sketch the direction and amplitude of the E-field vectors of light passed through the first polarizer

light source

0
0

45o

Page 8 of 8

Polarizer 1 Polarizer 2

0

Polarizer 3
Light sensor

b) Sketch the direction and amplitude of the E-field vectors the second and the third polarizer.

c) Is the resulting vector equal to zero? If not what is the direction of this vector? d) Read the explanation on site:

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polcross.html#c2

Explanation / Answer

A) E1= E0cos (theta)= E0 cos 0 = E0

B) E2=E1c0s (Theta)= E0 cos (45)= 0,7 E0

E3=E2cos (theta)=0,7E0 cos (45)= 0,49 E0

c) When a third polarizer is placed between the other two with its easy axis at 45 degrees to theirs, a remarkable thing happens. Some of the light that was blocked now gets through to the screen. The electric vector of the light coming from the first polarizer has a component that is parallel to the easy axis of the middle polarizer, so some of the light can pass through. The emerging light is now polarized at 45 degrees to its original direction and also to the easy axis of the next polarizer. The electric vector thus has a component that is parallel to this polarizer’s easy axis, and again some of it can pass through, illuminating the circular area on the screen

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