Virtual image
Virtual Vir"tu*al (?; 135), a. [Cf. F. virtuel. See {Virtue}.] 1. Having the power of acting or of invisible efficacy without the agency of the material or sensible part; potential; energizing. [1913 Webster]

Heat and cold have a virtual transition, without communication of substance. --Bacon. [1913 Webster]

Every kind that lives, Fomented by his virtual power, and warmed. --Milton. [1913 Webster]

2. Being in essence or effect, not in fact; as, the virtual presence of a man in his agent or substitute. [1913 Webster]

A thing has a virtual existence when it has all the conditions necessary to its actual existence. --Fleming. [1913 Webster]

To mask by slight differences in the manners a virtual identity in the substance. --De Quincey. [1913 Webster]

{Principle of virtual velocities} (Mech.), the law that when several forces are in equilibrium, the algebraic sum of their virtual moments is equal to zero.

{Virtual focus} (Opt.), the point from which rays, having been rendered divergent by reflection of refraction, appear to issue; the point at which converging rays would meet if not reflected or refracted before they reach it.

{Virtual image}. (Optics) See under {Image}.

{Virtual moment} (of a force) (Mech.), the product of the intensity of the force multiplied by the virtual velocity of its point of application; -- sometimes called {virtual work}.

{Virtual velocity} (Mech.), a minute hypothetical displacement, assumed in analysis to facilitate the investigation of statical problems. With respect to any given force of a number of forces holding a material system in equilibrium, it is the projection, upon the direction of the force, of a line joining its point of application with a new position of that point indefinitely near to the first, to which the point is conceived to have been moved, without disturbing the equilibrium of the system, or the connections of its parts with each other. Strictly speaking, it is not a velocity but a length.

{Virtual work}. (Mech.) See {Virtual moment}, above. [1913 Webster]


The Collaborative International Dictionary of English. 2000.

Look at other dictionaries:

  • Virtual image — Image Im age ([i^]m [asl]j; 48), n. [F., fr. L. imago, imaginis, from the root of imitari to imitate. See {Imitate}, and cf. {Imagine}.] 1. An imitation, representation, or similitude of any person, thing, or act, sculptured, drawn, painted, or… …   The Collaborative International Dictionary of English

  • virtual image — n an image (as seen in a plane mirror) formed of virtual foci * * * a picture from projected light rays that are intercepted before focusing, as by a plane mirror; it cannot be received on a screen, and it has the same orientation as the object.… …   Medical dictionary

  • virtual image — n. an optical image from which light rays appear to diverge, although they actually do not pass through the image * * * …   Universalium

  • virtual image — n. an optical image from which light rays appear to diverge, although they actually do not pass through the image …   English World dictionary

  • Virtual image — In optics, a virtual image is an image in which the outgoing rays from a point on the object never actually intersect at a point. A simple example is a flat mirror where the image of oneself is perceived at twice the distance from yourself to the …   Wikipedia

  • virtual image — menamasis vaizdas statusas T sritis fizika atitikmenys: angl. apparent image; virtual image vok. scheinbares Bild, n; virtuelles Bild, n rus. мнимое изображение, n pranc. image virtuelle, f …   Fizikos terminų žodynas

  • virtual image — noun Date: 1859 an image (as seen in a plane mirror) formed of points from which divergent rays (as of light) seem to emanate without actually doing so …   New Collegiate Dictionary

  • virtual image — noun a reflected optical image (as seen in a plane mirror) • Hypernyms: ↑reflection, ↑reflexion …   Useful english dictionary

  • Virtual image — Действительное изображение …   Краткий толковый словарь по полиграфии

  • Virtual — Vir tu*al (?; 135), a. [Cf. F. virtuel. See {Virtue}.] 1. Having the power of acting or of invisible efficacy without the agency of the material or sensible part; potential; energizing. [1913 Webster] Heat and cold have a virtual transition,… …   The Collaborative International Dictionary of English

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