Critical Opalescence

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critical opalescence

[′krid·ə·kəl ‚ōp·ə′les·əns]
Extreme opalescence resulting from strong density fluctuations in a medium near a critical point.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Opalescence, Critical


the abrupt intensification of scattering of light by pure substances in critical states, and also by solutions of liquids or gases when they reach the critical points of solubility.

Critical opalescence was explained in 1908 by M. Smoluchow-ski, who showed that the compressibility of a substance increases sharply at the critical temperature. As a result, the energy of thermal motion of the substance’s particles becomes sufficient for an “abrupt” intense increase in the number of microscopic regions in which the density of the substance deviates significantly from the average value (density fluctuations). Each such fluctuation is a disruption of the optical uniformity of the medium (a change in the index of refraction of the medium in a particular microvolume). The sharp increase in the number of fluctuations accompanying critical opalescence causes a medium that is virtually transparent at temperatures above and below the critical temperature to become a turbid medium.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
A discussion of each physical feature follows: (1) the thermal spectrum, (2) limb darkening, (3) solar collapse, (4) the solar density, (5) seismic activity, (6) mass displacement, (7) the chromosphere and critical opalescence, (8) shape, (9) surface activity, (10) photospheric/coronal flows, (11) photospheric imaging, (12) the solar dynamo, and (13) the presence of Sun spots.
Critical opalescence occurs when a material is placed at the critical point, that combination of temperature, pressure, magnetic field and gravity wherein the gas/liquid interface disappears.

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