Unpolarized light of intensity I0 is sent through 4 polarizers, each of the last three rotated 30o from the previous polarizer so that the last polarizer is perpendicular to the first. What is the intensity transmitted by this system?
1) 0.75 I0
2) 0.50 I0
3) 0.42 I0
4) 0.21 I0
5) 0.00