image

image in optics, likeness or counterpart of an object produced when rays of light coming from that object are reflected from a mirror or are refracted by a lens . An image of an object is also formed when this light passes through a very small opening like that of a pinhole camera (which has no lens). Images are classed as real or virtual. A real image occurs when the rays of light from the object actually converge to form an image and can be seen on a screen placed at the point of convergence. For example, the image produced by the refraction of light rays by a convex lens (when the distance between the object and the lens is greater than the focal length of the lens) is real, and it appears on the side of the lens opposite the one on which the object is present. On the other hand, a virtual image occurs when the prolongations of the light rays converge to form an image, but the light rays themselves do not reach the point of convergence. Thus a virtual image cannot be seen on a screen. The image in a plane mirror is virtual. It appears to be behind the mirror, at a distance equal to that of the object in front, although the rays of light from the object do not penetrate the mirror but are reflected from it. Images of the same size as the object are sometimes produced, as in the case of the plane mirror, but in other cases they are larger, and in still others, smaller. They are sometimes erect and in other cases are inverted. The size of the image and whether it is erect or inverted, real or virtual, depend on the distance of the object from the lens or mirror relative to the focal length and on the type of lens or mirror (plane, convex, or concave) employed.

im·age / ˈimij/ • n. a representation of the external form of a person or thing in sculpture, painting, etc. ∎  a visible impression obtained by a camera, telescope, microscope, or other device, or displayed on a video screen. ∎  an optical appearance or counterpart produced by light or other radiation from an object reflected in a mirror or refracted through a lens. ∎  Math. a point or set formed by mapping from another point or set. ∎  a mental representation or idea: he had an image of Uncle Walter throwing his crutches away. ∎  a simile or metaphor: he uses the image of a hole to describe emotional emptiness. ∎  the general impression that a person, organization, or product presents to the public: she strives to project an image of youth. ∎  [in sing.] a person or thing that closely resembles another: he's the image of his father. ∎  [in sing.] semblance or likeness: we are made in the image of God. ∎  (in biblical use) an idol. • v. [tr.] make a representation of the external form of: artworks that imaged women's bodies. ∎  (usu. be imaged) make a visual representation of (something) by scanning it with a detector or electromagnetic beam: every point on the Earth's surface was imaged by the satellite | [as n.] (imaging) medical imaging. ∎  form a mental picture or idea of: it is possible for us to image a society in which no one committed crime. DERIVATIVES: im·age·less adj.