Question

"Vehicles in this mirror are closer than they appear". Why is this warning printed on the side view mirror of most vehicles ?

Answer 1

The mirrors used are convex mirrors and so the image formed in the mirror is always virtual and diminished ( small in size). Hence the cars appear to small and far away than their actual physical positions.
Hope it helps!
thanks!

Answer 2

The mirrors which are used to manufacture side mirrors of any vehicle,is mandatorily a convex mirror.

That's why the reflection on that convex mirror is much smaller and further from the size and position of the real object.

This is done for safety purposes and to avoid car accidents.