rarefied adj

1 having low density; "rare gasses"; "lightheaded from the rarefied mountain air" [syn: rare, rarified]

2 reserved for an elite group [syn: rarified]

3 of high moral or intellectual value; elevated in nature or style; "an exalted ideal"; "argue in terms of high-flown ideals"- Oliver Franks; "a noble and lofty concept" [syn: exalted, high-flown, high-minded, lofty, rarified, idealistic, noble-minded]rarefy

1 lessen the density or solidity of; "The bones are rarefied"

2 make more subtle or refined [syn: sublimate, subtilize]

3 weaken the consistency of (a chemical substance) [syn: attenuate] [also: rarefied]rarefied See rarefy

English

Alternative spellings

• rarified

Adjective

1. Esoteric.
2. In the context of "of a gas etc.": Less dense than usual.

   The air at the top of a high mountain is rarefied.

Translations

• Spanish: rarificado, enrarecido

This page is about the physical process. For the ecological technique, see Rarefaction (ecology)

Rarefaction is the reduction of a medium's density, or the opposite of compression.

A natural example of this is as a phase in a sound wave or phonon. Half of a sound wave is made up of the compression of the medium, and the other half is the decompression or rarefaction of the medium.

Another natural example of rarefaction is in the layers of our atmosphere. Because what constitutes our atmosphere has mass, it is definite that most of the atmospheric matter will be nearer to the Earth. Therefore, air at higher layers of the atmosphere is considered to have less pressure, or is rarefied in relation to air at lower layers.

Rarefaction can be easily observed by compressing a spring and releasing it.

Rarefaction waves expand with time; for most gases the rarefaction wave keeps the same overall profile at all times (it is a 'self-similar expansion'). Each part of the wave travels at the local speed of sound, in the local medium. This expansion behaviour is in contrast to the behaviour of pressure increases, which get narrower with time, until they steepen into shock waves.

Rarefaction can refer to an area of low relative pressure following a shockwave.

See also

• Prandtl-Meyer expansion fan

External links

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