refraction

refraction

1. Physics the change in direction of a propagating wave, such as light or sound, in passing from one medium to another in which it has a different velocity

2. the amount by which a wave is refracted

3. the ability of the eye to refract light

4. the determination of the refractive condition of the eye

5. Astronomy the apparent elevation in position of a celestial body resulting from the refraction of light by the earth's atmosphere

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

refraction

(ri-frak -shŏn) A phenomenon occurring when a beam of light or other wave motion crosses a boundary between two different media, such as air and glass. On passing into the second medium, the direction of motion of the wave is ‘bent’ toward or away from the normal (the line perpendicular to the surface at the point of incidence). The incident and refracted rays and the normal all lie in the same plane. The direction of propagation is changed in accordance with Snell's law:

n ₁ sin i = n ₂ sin r

i and r are the angles made by the incident and refracted ray to the normal; n ₁ and n ₂ are the refractive indices of the two media. The change in direction of motion results from a change of wave velocity as the wave passes from the first to the second medium.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

refraction

[ri′frak·shən]

(electromagnetism)

The change in direction of lines of force of an electric or magnetic field at a boundary between media with different permittivities or permeabilities.

(physics)

The change of direction of propagation of any wave, such as an electromagnetic or sound wave, when it passes from one medium to another in which the wave velocity is different, or when there is a spatial variation in a medium's wave velocity.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

refraction

The change in direction of a light ray or a sound ray in passing from one medium to another.

McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

refraction

The bending of electromagnetic waves as they pass between materials with different refractive indices. Refraction is an important characteristic of optical systems. As light rays travel at a more perpendicular angle to the edge of a medium, they are refracted outside the medium rather than being reflected inside. See refractive index, total internal reflection and diffraction.

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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Refraction

 

The Russian words refraktsiia and prelomlenie may both be translated as “refraction.” When used with respect to light, refraktsiia in the broad sense has the same meaning as prelomlenie—that is, the change in the direction of light rays when the index of refraction of the medium through which the rays pass changes (seeREFRACTION OF LIGHT). For historical reasons, refraktsiia is more often used when characterizing the propagation of optical radiation in media whose index of refraction varies continuously from point to point; the paths of light rays in such media are smooth curves. The term prelomlenie is more often applied to the case where there is an abrupt change in the direction of light rays at the interface of two homogeneous media with different indexes of refraction. The term refraktsiia is by tradition used in a number of branches of optics, including atmospheric optics, eyeglass optics, and the optics of the eye.

The eye is an optical system that refracts light. A commonly used measure of the power of the eye as a refracting system is the eye’s power under suspension of accommodation. The principal refracting elements of the eye are the cornea and the lens. The power of these elements varies from 52.59 to 71.30 diopters; the average value is 59.92 diopters. In the normal, or emmetropic, eye, the power of the eye is matched to its dimensions. This means that parallel rays of light that enter the eye are focused at the center of the retina in the region of the macula lutea. A clear image of the object being viewed is then obtained on the retina—a situation that is a necessary condition for good vision.

Errors in refraction result in myopia or hyperopia. The power of accommodation of the eye changes with age: it is less than normal in infants and may again decrease in old age. This change in accommodation power with advancing age is called presbyopia. Anomalies in refraction cannot be treated through medication. Special systems of optical lenses (eyeglasses) are used to correct vision when errors of refraction exist.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.