Unpolarized light of intensity $I$ is incident on a system of two polarizers,$A$ followed by $B$. The intensity of emergent light is $I/2$. If a third polarizer $C$ is placed between $A$ and $B$,the intensity of emergent light is reduced to $I/3$. The angle between the polarizers $A$ and $C$ is $\theta$. Then:

• A
  $\cos \theta = (2/3)^{1/4}$
• B
  $\cos \theta = (1/3)^{1/4}$
• C
  $\cos \theta = (1/3)^{1/2}$
• D
  $\cos \theta = (2/3)^{1/2}$