Figure shows a torch sending a parallel beam of light fixed on a wall and a plane mirror which forms a spot on the wall. As the mirror moves towards the wall, the spot on the wall moves

White light is incident on the interface of glass and air as shown in the figure. If green light is just totally internally reflected then the emerging ray in air contains

In a spherical paper weight $\left(R=10 \mathrm{cm}\right)$ made of glass of refractive index $\mu =\frac{3}{2}$, an object is embedded at a distance $5 \mathrm{cm}$ from its centre. What is the apparent position of the object when seen from the opposite side (see figure)?

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