Question

An unpolarized beam of light is incident on a pair of polarizing filters. The first filter set to polarize in the vertical direction and the second filter is set to polarize 38° from vertical. What is the intensity of the light beam after the second filter relative to the original beam?

Answer 1

To solve this problem you have to know about Polarizer and Malus's Law

Step 1.

Definition: Is an optical filter that passes light of a specific polarization and blocks waves of other polarizations.It can convert a beam of light of undefined or mixed polarization into a beam with well-defined polarization, polarized light.

Malus's Law: which is named after Étienne-Louis Malus, says that when a perfect polarizer is placed in a polarized beam of light, the intensity, I, of the light that passes through is given by   

where I₀ is the initial intensity, and θ_i is the angle between the light's initial polarization direction and the axis of the polarizer. A beam of unpolarized light can be thought of as containing a uniform mixture of linear polarizations at all possible angles. Since the average value of is 1/2, the transmission coefficient becomes

  

Step 2.

ANSWERS:

How you can read in the above definition the intensity during the first polarizing filter is the following:

  

The intensity for the second polarizing filter is:

If you have any question pleaselet me know in the comments