Question

A series of polarizers are each placed at a 8.0 ∘ interval from the previous polarizer. Unpolarized light is incident on this series of polarizers. How many polarizers does the light have to go through before it is below 1/10 of its original intensity?

Answer 1

let Io is the intensity of unpolarised light.

Intensity through 1st polariser, I1 = Io/2

Intensity through 2nd polariser,

I2 = I1*cos^2(theta)

= (Io/2)*cos^2(theta)

intensity through 3rd polariser,

I3 = I2*cos^2(theta)

= (Io/2)*cos^2(theta)*cos^2(theta)

= (Io/2)*(cos(theta))^(2*2)

Intensity through nth polariser,

In = (Io/2)*(cos(theta))^(2*(n-1))

Io/10 = (Io/2)*(cos(8))^(2*(n-1))

1/5 = cos(8)^(2*(n-1))

1/5 = 0.990268^(2*(n-1))

on solving the above equation we get,

==> n = 83 <<<<<<<<<------------------Answer