## University Physics with Modern Physics (14th Edition)

$0.375I_0$.
The first polarizer filters out half the incident light. $$I_1=\frac{1}{2}I_o$$ The fraction filtered out by the second polarizer depends on the angle between the axes of the two filters, which is 30 degrees. $$I_2=I_1cos^2\theta=\frac{1}{2}I_o cos^230^{\circ}=0.375I_0$$