emissivity

American  

[em-uh-siv-i-tee, ee-muh-] / ˌɛm əˈsɪv ɪ ti, ˈi mə- /

noun

Thermodynamics.

1. the ability of a surface to emit radiant energy compared to that of a black body at the same temperature and with the same area.

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emissivity British  

/ ˌɛm-, ɪmɪˈsɪvɪtɪ /

noun

1.  ε.  a measure of the ability of a surface to radiate energy; the ratio of the radiant flux emitted per unit area to that emitted by a black body at the same temperature

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Etymology

Origin of emissivity

First recorded in 1875–80; emissive + -ity

Example Sentences

Efficient cooling requires high reflectivity in the former range to minimise the solar heat gain and high emissivity in the latter range to maximise the radiative heat dissipation.

From Science Daily • Nov. 10, 2023

Reionization after Planck: the derived growth of the cosmic ionizing emissivity now matches the growth of the galaxy UV luminosity density.

From Nature • May 15, 2018

An ideal radiator is one that has an emissivity of 1 at all wavelengths and, thus, is jet black.

From Textbooks • Aug. 12, 2015

Water molecules rotate and vibrate particularly well at infrared frequencies, emitting and absorbing them so efficiently that the emissivity for skin is e = 0.97 in the infrared.

From Textbooks • Aug. 12, 2015

Two Lehner mantles which have now been burning continuously in my laboratory for over 3,000 hours give at this moment a brighter light emissivity than most of the Welsbachs do in their prime.'

From Researches on Cellulose 1895-1900 by Cross, C. F.