Real image 

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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 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 a human retina (the latter two pass light through an internal convex lens).

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.

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 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 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]

See also