The image formed by a lens is due to which optical phenomenon?

$A$ beam of light is incident through the holes on side $A$ and emerges out of the holes on the other face of the box as shown in the Figure. Which of the following could be inside the box?

The mirror outside the driver's 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?

In a plane mirror,the distance between the image and the mirror is the same as the distance between the object and the mirror.

Where should an object be placed in front of a convex lens to obtain an image on the same side as the object?

$A$ convex mirror always forms a virtual and erect image.