7. Unpolarized light is passed through three successive Polaroid filters, each with its transmission axis at 45.0° to the preceding filter. What percentage of light gets through?

 

Unpolarized light lost ½ of the initial intensity I₀ after the first Polaroid filter.

To calculate the changes of the light intensity on the second and the third filters we have to use the formula 38.9

I _passed = I _preceding cos² θ = I _preceding cos² 45^ο = I _preceding ½

So, after the first filter: I₁=I₀/2,

After the second filter: I₂=I₁/2= I₀/4

After the third filter: I₃=I₂/2=I₀/8

Solution: 100%/8 = 12.5% of the initial light (intensity) gets through.