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

An equiconvex lens of $\mu =1.5$ and radius of curvature $R=20 \mathrm{cm}$ is placed in front of a convex mirror of radius of curvature $20 \mathrm{cm}$ as shown. An object is placed as indicated. The possible value of $x$ so that the image coincides with the object is

The refractive index of a slab of length $21$ changes as $\mu =\left\{\begin{array}{l}{\mu }_0\frac{x}{1},0\le x\le 1\\ {\mu }_0\frac{x^2}{1^2},I\le x\le 2I\end{array}\right.$where $x$ is measured from left and the equivalent refractive index of the slab would be

An object $AB$ of height $1 \mathrm{cm}$ is moving towards the lens with constant velocity $10 {\mathrm{ms}}^{-1}$ as shown. The velocity of image of point $B$ at the given instant is

A small object is moving towards a plane mirror with velocity $V_1=10 {\mathrm{ms}}^{-1}$ and the plane mirror is moving with velocity $V_2=5 {\mathrm{ms}}^{-1}$ as shown. The speed of image is