A tank contains a transparent liquid of refractive index $\mu .$ The bottom of the tank is a plane mirror as shown. A person at $P$ looks at an object $O$ and its image in the mirror. The distance between the object and its image in the mirror as perceived by the person is

An object is placed $1.5 \mathrm{m}$ in front of the curved surface of a planoconvex lens whose flat surface is silvered. A real image is formed $300 \mathrm{cm}$ in front of the lens. The focal length of the lens is

Two prisms of same glass $(\mu =\sqrt{2})$ are stuck together without gap as shown. Find the angle of incidence $i$ on the face $AC$ such that the deviation produced by the combination is minimum

Two plane mirrors $M_1$ and $M_2$ intersecting at point $O$ forming an angle of $60°.$ The distance between the two direct images of a point object $\text{'}P\text{'}$ formed by them is $10 \mathrm{cm}.$ The distance $OP$ is