In the figure shown, the image of a real object $O$ is formed at point $I$. $AB$ is the principal axis of the mirror. The mirror must be:

$AB$ is an incident beam of light and $CD$ is a reflected beam (the number of reflections for this may be $1$ or more than $1$) of light. $AB$ and $CD$ are separated by some distance (may be large). It is possible by placing what type of mirror on the right side.

A $U$-shaped wire is placed before a concave mirror having a radius of curvature $20 \mathrm{cm}$ as shown in the figure. Find the total length of the image.

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 :