An optical image is the spatial reproduction of an object formed by a system of light rays or electromagnetic waves. In geometrical optics, a real optical image occurs where rays from each object point converge; a virtual optical image occurs where backward extensions of the rays appear to meet.
A converging lens can project a real image onto a screen when the object lies beyond its focal length. The upright image seen in a plane mirror is virtual and cannot be caught on a screen at its apparent location. Diffraction and optical aberration limit the point-to-point idealization.
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