The point(s) from which light rays converge as they emerge from a lens or mirror. The rays do not actually pass through each image point. [One and only one ray, the one that passes through the center [..]

An image from a lens or mirror that cannot be brought to focus on a screen.

An image that only appears to be formed by rays of light.

The point(s) from which light rays converge as they emerge from a lens or mirror. The rays do not actually pass through each image point, but diverge from it. See: real image.

An image where light rays appear to originate from a mirror or lens; this image cannot be projected on a screen

An image that is not the actual source of real light rays, for example the image seen in a mirror appears to be behind the mirror.

A copy of an image that is formed at the place from where the light rays seem to come (Lesson 22)

A measure of the ability of an observer to see objects at a distance through the atmosphere. A measure of this property is expressed in units of distance. This term should not be confused with VISUAL [..]

an image that forms at a point from which light rays appear to come but do not actually come