Virtual image

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 mirror. That is, if you are half a meter in front of the mirror, your image will appear at a distance of half a meter inside or behind the mirror.

To contrast, a real image is an image in which the outgoing rays from a point on the object pass through a single point. It is easiest to observe real images when projected on an opaque screen. A screen is not necessary for the image to form. [cite book | last = Knight | first = Randall D. | title = Five Easy Lessons: Stategies for successful physics teaching | year = 2002 | publisher = Addison Wesley | pp=276-277]

* When we look through a diverging lens (at least one concave surface) or look into a convex mirror, what we see is a virtual image. However, if we observe a focused image on a screen inside or behind a converging lens (at least one convex side) or in front of a concave mirror what we see on the screen is a real image because the image really is at the screen's location. If we position ourselves so that the screen is directly between ourselves and the optical device (mirror, lens, etc.), we can remove the screen and still observe the image. It is also important to note that a converging lens and concave mirror are also capable of producing virtual images if the object is within the focal length.

* For example, a plane or mirror forms a virtual image positioned behind the mirror. Although rays of light seem to come from behind the mirror, light from the source spreads and exists only in front of the mirror. In drawings of optical systems, virtual rays are conventionally represented by dotted lines. Optical rays represent paths on which light actually travels. A virtual ray (the dotted lines) represent perceived paths as seen by an observer looking into the optical device. The light rays do not travel on these dotted paths. A point on the image is located where the virtual rays intersect.

ee also

*Real image
*Mirror image
*Reflection
*List of optical topics

References


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Look at other dictionaries:

  • 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… …   The Collaborative International Dictionary of English

  • 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 — 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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