The image of the distant illuminated building projected onto a piece of heavy, white cardboard by a small reflecting telescope is a real image. This is because it is formed by the actual convergence of light rays after being reflected by the telescope's mirror.
The image of an automobile in a flat rearview mirror is a virtual image. Virtual images are formed when light rays appear to diverge from a point behind the mirror, creating the illusion of an image without the light rays actually converging at that point.
The image of shop aisles in a convex observation mirror is also a virtual image. Convex mirrors are curved outward and always produce virtual images because the light rays diverge after reflection, giving the illusion of an image that is not formed by the actual convergence of light rays.
