Top: The formation of a real image using a convex lens. Bottom: The formation of a real image using a concave mirror. In both diagrams, f is the focal point, O is the object and I is the image. Solid blue lines indicate light rays. It can be seen that the image is formed by actual light rays and thus can form a visible image on a screen placed at the position of the image.
A convex lens gathers light from different regions of the object onto different regions of the detector or retina, producing a real image. Each region of the detector or retina indicates the light produced by a corresponding region of the object.
In optics, a real image is a representation of an actual object (source) formed by rays of light passing through the image. If a screen is placed in the plane of a real image the image will generally become visible. Examples of real images include the image seen on a cinema screen, the image produced on a detector in the rear of a camera, and the image produced on a human retina.
When we see through a lens, or look into a convex or concave mirror, what we see is not a real image. This, the image that we see on the other side of the lens or mirror plane, is known as a virtual image.
Real rays of light are always represented by full, solid lines. A real image occurs where rays converge, whereas a virtual image occurs where rays only appear to converge.
A real image is exemplified by a science toy/demonstration called "Mirage" which consists of two facing parabolic mirrors. One faces up, the other faces down one 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]
