The mirror outside the driver side of a vehicle is usually a convex mirror. Printed on such a mirror is usually the warning “Vehicles in this mirror are closer than they appear”. What is the reason for this warning ?
The reason for this warning is that the virtual image produced in a convex mirror is reduced in size and, therefore, looks smaller, just as a distant object will appear in a plane mirror. An unwary driver, thinking that the side-view mirror is a plane mirror, might incorrectly deduce from the small size of the image, that the vehicle behind is far enough away to ignore.