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Greater than normal refraction, particularly as related to the atmosphere. Less than normal refraction is called SUB-REFRACTION.

Related Terms

REFRACTION

The change of direction or speed of light as it passes from one medium to another.

IONOSPHERIC CORRECTION

A correction for ionospheric refraction, a major potential source of error in all satellite radionavigation systems. Navigation errors can result from the effect of refraction on the measuremen

LAURENCE

A shimmering seen over a hot surface on a calm, cloudless day, caused by the unequal refraction of light by innumerable con- vective air columns of different temperatures and densities.

ANGLE OF DEVIATION

The angle through which a ray is bent by refraction

BAROMETRIC PRESSURE CORRECTION

A correction due to nonstandard baro- metric pressure, particularly the sextant altitude correction due to changes in refraction caused by difference between the actual baro- metric pressure and the standard barometric pressure used in the computation of the refraction table.

ATMOSPHERIC REFRACTION

Refraction resulting when a ray of radiant energy passes obliquely through the atmosphere. It may be called astronomical refraction if the ray enters the atmosphere from outer space, or terrestrial refraction if it emanates from a point on or near the surface of the earth.

CRITICAL ANGLE

1. The maximum angle at which a radio wave may be emitted from an antenna, in respect to the plane of the earth, and still be returned to the earth by refraction or reflection by an ionospheric layer. 2. The angle at which radiation, about to pass from a medium of greater density into one of lesser density, is refracted along the surface of the denser medium.

DISPERSION

The separation of light into its component colors by its passage through a diffraction grating or by refraction such as that provided by a prism

HALO

Any of a group of optical phenomena caused by refraction or reflection of light by ice crystals in th

MIRAGE

An optical phenomenon in which objects appear distorted, displaced (raised or lowered), magnified, multiplied, or inverted due to varying atmospheric refraction when a layer of air near the earth’s surface differs greatly in density from surrounding air.

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