Two polaroids are oriented with their principal planes making an angle of $60^\circ$. Then the percentage of incident unpolarized light which passes through the system is:
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Always remember: First polaroid $\rightarrow$ divide by 2. Second polaroid $\rightarrow$ multiply by $\cos^2 \theta$. For $60^\circ$, $\cos^2(60^\circ)$ is $0.25$ or $1/4$. Half of $1/4$ is $1/8$, which is $12.5%$.