The refracting angle of a prism is $A$ and the refractive index of material of the prism is $\cot \left(\frac{A}{2}\right)$. The angle of minimum deviation is 

A light ray is incident on face $AB$ of prism $ABC$ as shown in the figure. The second prism is kept in such a manner that emergent ray from prism $ABC$ is falling normally on face $A\text{'}B\text{'}$of prism$A\text{'}B\text{'}C\text{'}$. The net deviation produced by the optical system of the two prisms is

A ray of light from a liquid $\left(\mu =\sqrt{3}\right)$ is incident on a system of two right-angled prisms of refractive indices $\sqrt{3}$ and $\sqrt{2}$ as shown. The ray suffers zero deviation when it emerges into the air from $CD$. The angle of incidence $i$ is: