Two polarisers P_1 and P_2 are placed in such a way that the intensity of the transmitted light will be zero. A third polariser P_3 is inserted in…

Two polarisers $\displaystyle P_1$ and $\displaystyle P_2$ are placed in such a way that the intensity of the transmitted light will be zero. A third polariser $\displaystyle \mathrm{P}_3$ is inserted in between $\displaystyle \mathrm{P}_1$ and $\displaystyle \mathrm{P}_2$, at particular angle between $\displaystyle \mathrm{P}_2$ and $\displaystyle \mathrm{P}_3$. The transmitted intensity of the light passing the through all three polarisers is maximum. The angle between the polarisers $\displaystyle \mathrm{P}_2$ and $\displaystyle \mathrm{P}_3$ is :