Unpolarized light of intensity I passes through an ideal polarizer A.

Unpolarized light of intensity I passes through an ideal polarizer A. Another identical polarizer $\mathrm{B}$ is placed behind $\mathrm{A}$. The intensity of light beyond $\mathrm{B}$ is found to be $\frac{1}{2}$. Now another identical polarizer $\mathrm{C}$ is placed between $\mathrm{A}$ and $\mathrm{B}$. The intensity beyond $\mathrm{B}$ is now found to be $\frac{\mathrm{I}}{8}$. The angle between polarizer $\mathrm{A}$ and $\mathrm{C}$ is :