The focal length of a plane mirror is .......

$A$ man runs towards a plane mirror at a speed of $15 \ m/s$. What is the speed of his image relative to the mirror? (in $m/s$)

The angle made by the incident ray of light with the reflecting surface is called:

Find the angle of deviation for the given diagram.

The following figure shows the multiple reflection of a light ray along a glass corridor where the walls are either parallel or perpendicular to one another. If the angle of incidence at point $P$ is $30^o$,what are the angles of reflection of the light ray at points $Q, R, S$ and $T$ respectively?

An object is fixed at the bottom of a vessel and water is filled in the vessel up to a height of $10 \,cm$. $A$ plane mirror is placed at a height of $7 \,cm$ from the surface of water in such a way that its reflecting surface faces the water. The distance of the image from the mirror is (Refractive index of water,$n=1.33$). (in $\,cm$)