1. The problem statement, all variables and given/known data I need some help understanding the following solved problem: If light that is initially natural and of flux density ##I_i## passes through two sheets of HN-32 whose transmission axes are parallel, what will be the flux density of the emerging beam? Solution: ##64 \% (32 \% \ I_i) = 21 \% I_i## leaves the second filter. I don't understand where the "64%" term comes from. 3. The attempt at a solution If I understand correctly, using a HN-32 sheet means that each filter passes 32% of the incident light. So when natural light enters the first one only 32% leaves it so a flux density of ##32 \% \ I_i## enters the second filter. This light is a P-state or linearly polarized. So I guess the second sheet must take away another 32%, right? And the rest of the light (68%) must have been tilted toward the extinction axis so it didn't make it through. Therefore I get 32%(32%Ii). So how did they get that answer, and where did the 64% come from?