An object and a concave mirror are approaching each other with velocities $\mathrm{10\; m/s}$ and $\mathrm{5\; m/s}$ as shown in figure. The velocity of image of object at the instant shown in figure is

In the figure shown, find the total magnification after two successive reflections first on $M_1$ and then on $M_2$.

A short linear object $\mathrm{O}$ is placed on the principal axis of convex mirror of focal length $f$ as shown in the figure. The ratio of transverse magnification to longitudinal magnification is :

A diverging lens of focal length $-10 \mathrm{cm}$ is moving towards right with a velocity $5 \mathrm{m} {\mathrm{s}}^{-1}$. An object placed on the principal axis is moving towards left with a velocity $3 \mathrm{m} {\mathrm{s}}^{-1}$. The velocity of the image at the instant when the lateral magnification produced is $\frac{1}{2}$, is (All velocities are with respect to ground)