Question

why do we prefer a convex mirror as a rear view mirror in vehicles

Answer 1

Convex mirrors are preferred as rear view mirror in vehicles as: 
* It forms an erect image of an object hence object becomes easily identified. 
* It forms a diminished image of object thus increases the field of vision.
Object that are far away from us are seen closer which helps us to take early decision while driving.
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Answer 2

Convex mirror are commonly used as rear view mirror because :

They give an,

ERECT

VIRTUAL

FULL SIZED DIMINISHED IMAGE

Thus convex mirror enable to driver to view much larger area than would be possible with a plane mirror