Real image
In optics, a real image is a representation[ambiguous] of an object (source) in which the perceived location is actually a point of convergence of the rays of light that make up the image. If a screen is placed in the plane of a real image the image will generally become visible on the screen. Examples of real images include the image seen on a cinema screen (the source being the projector), the image produced on a detector in the rear of a camera, and the image produced on an eyeball retina (the camera and eye focus light through an internal convex lens). In ray diagrams (such as the images on the right), real rays of light are always represented by full, solid lines; perceived or extrapolated rays of light are represented by dashed lines. A real image occurs where rays converge, whereas a virtual image occurs where rays only appear to converge.
Real images can be produced by concave mirrors and converging lenses if and only if the object is placed further away from the mirror/lens than the focal point and this real image is inverted. As the object approaches the focal point the image is approaching infinity, and when the object passes the focal point the image becomes virtual and is not inverted.
When we look into a convex mirror or see through a concave lens, what we see is not a real image. This image, which appears to be on the other side of the lens or mirror plane, is known as a virtual image.
A real image is exemplified by a science toy/demonstration called "Mirage" which consists of two facing parabolic mirrors: one faces up, the other one faces down with a hole at its center. A real image of an object at the apex of the lower mirror appears just above the hole in the upper mirror.[1]
