Question

Light that is already vertically polarized enters a 2 polaroid system. The first polaroid is tilted 10 degrees from the vertical and the second is tilted 65 degrees from the vertical. What fraction of the incoming light makes it through the set of polaroids?

The answer should be 0.319.

Please explain and show your work.

Thank you.

Answer 1

Use Malu' law

the component of electric field which passes through the polarizer is:

where the angle is between the initial polarization of light and the angle of the polarizer

so, the intensity will be:

after the first polarizer, the fraction of intensity which passes would become:

the polarization is now no more vertical but instead 10 degrees from vertical.

This is now incident on a polarizer whose axis makes 65 degrees from vertical. So, the angle between the two polarizers will be: 65 - 10 = 55^o

so, the final fraction of intensity which makes it through both the polarizers will be:

= 31.907%.