Question

How will you distinguish between a plane mirror, concave mirror and a convex mirror, without touching them?

Answer 1

To distinguish between a plane mirror, concave mirror and a convex mirror, we take an object and keep it at varying distance from the mirror and notice the nature of the image formed.
If the image formed is always upright, virtual and the same size as the object then it is a plane mirror.
If the image formed is sometimes inverted, real and diminished, sometimes inverted, real and the same size as the object and sometimes is upright, virtual and enlarged. Then it is a concave lens.
If the image formed is always upright, virtual and diminished, then it is a convex mirror.