rarefaction

1 9.9

A drop in how much material is in a space, for example less air at high altitudes

noun
/ˌrɛəˈfækʃən/

Specialized

: rarefacción

A combination of gas acceleration and the compression and rarefaction phases of the seismic wave throws materials out of the crater at the surface.
compression and rarefaction

Examples

So these waves travel from the source to the ear in little waves of compression where the air is just compressed, and rarefaction where the air is spread out.
Send a high-intensity ultrasound wave through a container of liquid, and it's not surprising to find that the alternating cycles of acoustic compression and rarefaction create micron-sized bubbles in the liquid and cause them to successively expand and contract.

Academic text (2006)
The influence of water on the rarefaction wave in gold is restricted by the atmosphere.

Academic text (2018)
A rarefaction, the opposite, occurs when the object has moved away from the air molecules, leaving them further apart.

Academic text (2004)
The profile of the rarefaction wave resembles its profile in the case of gas.

Academic text (2018)
X-ray of the mastoid showed areas of rarefaction on the right side.

Academic text (2007)
As the wind blows, the net motion of the two spacecraft toward or away from each other will cause slight compression or rarefaction of the radio waves, from which the properties of the wind can be inferred.

Academic text (2004)
In sound waves, a rarefaction is the phase where air molecules are spread further apart, resulting in lower pressure.
The rarefaction of air occurs when it expands as the temperature increases, leading to a decrease in density.
During a rarefaction, the density of a gas decreases as the particles move away from each other.

Synonyms

low density

vsrarefaction

Specialized

1 3.7

A small amount of material in a space like foam or gas

refers to a drop in density inside a physical medium

thinness

vsrarefaction

1 4.3

Not being full or dense, like a small crowd and a small number of hairs

is specifically about density decreasing in materials like air or gas

Antonyms

compression

42 4.0

Pressing something so it becomes smaller and denser

compaction

1 6.5

Making soil or material denser by pressing it together

consolidation

Specialized

1 6.7

A hard mass that forms when loose material is pressed together

How Dense

solid

Specialized

9 1.0

atmosphere

406 3.5

rarefaction

Specialized

1 9.9

vacuum

Specialized

77 4.2

Surface Forms

rarefaction singular

rarefactions plural

Morphology

rarefaction = rarefy (semi-transparent) = rare + fy + ation

Formed from the verb 'rarefy' + the noun-forming suffix '-ation'; the technical sense depends on knowing 'rarefy' and the physics sense of 'rare' (less dense), so learners may only partially infer it.

Etymology

The word rarefaction comes from Latin parts rarus ('thin' or 'sparse') and facere ('to make') and is related to the English word rare ('not many' or 'not dense'). So a rarefaction is literally 'making thin', which is why it means an area where the air or gas becomes less dense.