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

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

An object $O$ is placed between two parallel plane mirrors $M_1$ and $M_2$. The distance of the object from $M_1$ is $6\,cm$ and from $M_2$ is $15\,cm$. The position of the $4^{th}$ image formed by mirror $M_1$ is:

Two plane mirrors are inclined at an angle of $72^{\circ}$. The number of images of a point object placed between them will be

$A$ plane mirror makes an angle of $30^\circ$ with the horizontal. If a vertical ray strikes the mirror,find the angle between the mirror and the reflected ray.

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 $\,cm$)