$n$ number of identical equilateral prisms are kept in contact as shown in figure. If deviation through a single prism is $\delta$. Then ( $n, m$ are integers)

A plane mirror is placed horizontally inside water $\left(\mu =\frac{4}{3}\right).$ A ray falls normally on it. The mirror is rotated by angle $\theta$ such that after reflection, the ray does not come out of water. The minimum value of $\theta$ is

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)?