Unpolarized light of intensity 100 mW/m² passes through two filters.The first filter has an alignment of 30.0 degrees from the vertical and the second has an alignment of 80.0 degrees from the vertical.What is the intensity of the light that passes through the second filter?

Question

Quizplus · Accepted Answer

The intensity of unpolarized light passing through a filter with an alignment angle θ is given by:
I = I0 cos2θ
where I0 is the initial intensity of the light. 
Thus, the intensity of the light passing through the first filter is
I1 = I0 cos2(30°) = I0(3/4)
The intensity of the light passing through the second filter is
I2 = I1 cos2(80°) = I0(3/4)cos2(80°)
Substituting the given values, we get
I2 = (100 mW/m2)(3/4)cos2(80°) = 21 mW/m2
Therefore, the answer is (C).

Unpolarized Light of Intensity 100 MW/m2 Passes Through Two Filters

Unpolarized Light of Intensity 100 MW/m² Passes Through Two Filters