Question

Which mirror is used as rear view mirror in automobile to see traffic behind and why this mirror is useful

Answer 1

Convex mirror for rear view of back side

Answer 2

Convex mirror is used as rear view mirror in automobiles to see traffic behind beacuse the image is smaller, more image can fit onto the mirror, so a convex mirror provides for a larger field of view than a plane mirror. This is why they are useful. They are used whenever a mirror with a large field of view is needed. For example, the passenger-side rear view mirror on a car is convex.