Misplaced Pages

Light

Article snapshot taken from Wikipedia with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.

This is an old revision of this page, as edited by 63.199.50.211 (talk) at 21:21, 20 October 2008 (→Theories about light). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Revision as of 21:21, 20 October 2008 by 63.199.50.211 (talk) (→Theories about light)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)
This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed.
Find sources: "Light" – news · newspapers · books · scholar · JSTOR (May 2007) (Learn how and when to remove this message)
For other uses, see Light (disambiguation).
File:PrismAndLight.jpg
A beam of white light (entering upwards from the right) is dispersed into its constituent colors by its passage through a prism. The fainter beam of white light exiting to the upper right has been reflected (without dispersion) off the first surface of the prism.

Light, or visible light, is electromagnetic radiation of a wavelength that is visible to the human eye (about 400–700 nm), or up to 380–750 nm. In the broader field of physics, light is often used to refer to electromagnetic radiation of all wavelengths, whether visible or not.

Three primary properties of light are:

Light can exhibit properties of both waves and particles (photons). This property is referred to as wave–particle duality. The study of light, known as optics, is an important research area in modern physics. hellomoto hdfjhsncorqwufn gzsczngtoeu grd

Refraction

Note, n = 1 in a vacuum and n > 1 in a transparent substance, where n is the index of refraction.

When a beam of light crosses the boundary between a vacuum and another medium, or between two different media, the wavelength of the light changes, but the frequency remains constant. If the beam of light is not orthogonal (or rather normal) to the boundary, the change in wavelength results in a change in the direction of the beam. This change of direction is known as refraction.

The refractive quality of lenses is frequently used to manipulate light in order to change the apparent size of images. Magnifying glasses, spectacles, contact lenses, microscopes and refracting telescopes are all examples of this manipulation.

Optics

Main article: Optics

The study of light and the interaction of light and matter is termed optics. The observation and study of optical phenomena such as rainbows and the aurora borealis offer many clues as to the nature of light as well as much enjoyment.

abdcubewgruertdtbw hkdsioa hxndquhdliuq penis

±wcoufskilk,zkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk aejqOHDSAKJBNALK JLKLKJLJOSDFJOKKSJKFOSMKFL;D;DPF,BGOSF,S;F;WQW'EP;;PG,DJNJCJSDKFNDKAOS,FI

Light pressure

Main article: Radiation pressure

Light pushes on objects in its way, just as the wind would do. This pressure is most easily explainable in particle theory: photons hit and transfer their momentum. Light pressure can cause asteroids to spin faster, acting on their irregular shapes as on the vanes of a windmill. The possibility to make solar sails that would accelerate spaceships in space is also under investigation.

Although the motion of the Crookes radiometer was originally attributed to light pressure, this interpretation is incorrect; the characteristic Crookes rotation is the result of a partial vacuum. This should not be confused with the Nichols radiometer, in which the motion is directly caused by light pressure.

Spirituality

File:Kallara Pazhyapalli Light.JPG
An intricate display for the feast of St.Thomas at Kallara Pazhayapalli in Kottayam, Kerala dramatically illustrates the importance of light in religion

The sensory perception of light plays a central role in spirituality (vision, enlightenment, darshan, Tabor Light), and the presence of light as opposed to its absence (darkness) is a common Western metaphor of good and evil, knowledge and ignorance, and similar concepts.

References

  1. Cecie Starr (2005). Biology: Concepts and Applications. Thomson Brooks/Cole. ISBN 053446226X.
  2. Kathy A. (02.05.2004). "Asteroids Get Spun By the Sun". Discover Magazine. {{cite web}}: Check date values in: |date= (help)
  3. "Solar Sails Could Send Spacecraft 'Sailing' Through Space". NASA. 08.31.2004. {{cite web}}: Check date values in: |date= (help)
  4. "NASA team successfully deploys two solar sail systems". NASA. 08.9.2004. {{cite web}}: Check date values in: |date= (help)
  5. P. Lebedev, Untersuchungen über die Druckkräfte des Lichtes, Ann. Phys. 6, 433 (1901).
  6. Nichols, E.F & Hull, G.F. (1903) The Pressure due to Radiation, The Astrophysical Journal,Vol.17 No.5, p.315-351

See also

Category: