virtual image

...When a bundle of light rays emitted from a point on an object intersects again at a point after being reflected and refracted by the optical system, the point on the object from which the bundle of light rays originates is called the object point, the point where they intersect again is called the image point, and the collection of image points is called an image. When a bundle of light rays that pass through an optical system actually converges at a single point, it is called a real image, and when the light rays intersect at a single point when extended in the opposite direction, it is called a virtual image. For example, the image of the sun formed by a convex lens is a real image, but the image reflected in a full-length mirror is a virtual image. ...

*Some of the terminology explanations that mention "virtual image" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…物体の1点から出た光線束が光学系による反射と屈折を経た後，再び1点で交わるとき，光線束の出る物体の1点を物点，再び交わる1点を像点といい，像点の集まったものを像と呼ぶ。光学系を通過した光線束が実際に1点に集まる場合を実像real image，光線を逆向きに延長したときに1点で交わる場合を虚像virtual imageという。例えば凸レンズによる太陽の像は実像であるが，姿見に映った像は虚像である。…

※「virtual image」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報