A linear object, $AC$ of length, $10 \mathrm{cm}$ is placed along the principal axis of a concave mirror of focal length, $10 \mathrm{cm}$ (see figure). $C$ is the centre of curvature of the mirror. The length of the image is

A point object is moving with speed $4 \mathrm{cm}{ \mathrm{s}}^{-1}$ in front of a combination of two plane mirrors (see figure). Velocity of image of the object formed by mirror $M_1$ relative to image formed by mirror $M_2$ is

A concave lens of radius of curvature $15 \mathrm{cm}$ and $\mu =1.5$ is placed in water $\left(\mu =\frac{4}{3}\right).$ If one surface is silvered, then image distance from lens when an object is placed at distance of $14 \mathrm{cm}$ from the lens is

A ray of ligand is incident perpendicularly on a prism and it follows the path as shown in figure. The minimum refractive index of the prism can be

A ray of light, moving parallel to $x$-axis is incident on a parabolic mirror at point $P$ as shown in figure. If angle of deviation suffered by the ray after reflection is $120°$, the $y$-coordinate of point $P$ is