emissivity

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Related to emissive: emissive power, Emissive layer

Emissivity

The ratio of the radiation intensity of a nonblack body to the radiation intensity of a blackbody. This ratio, which is usually designated by the Greek letter ε, is always less than or just equal to one. The emissivity characterizes the radiation or absorption quality of nonblack bodies. Published values are readily available for most substances. Emissivities vary with temperature and also vary throughout the spectrum. For an extended discussion of blackbody radiation and related information See Heat radiation.

A spectral emissivity of zero means that the heat radiator emits no radiation at this wavelength. Strongly selective radiators, such as insulators or ceramics, have spectral emissivities close to 1 in some parts of the spectrum, and close to zero in other parts. Carbon has a high spectral emissivity throughout the visible and infrared spectrum, exceeding 0.90 in certain portions; thus carbon is a good blackbody radiator. Tantalum is the only metal with a spectral emissivity greater than 0.5 in the visible spectrum. All other metals have a lower spectral emissivity. Tungsten is a relatively good emitter, with a spectral emissivity of 0.43–0.47 within the visible region of the spectrum. See Blackbody

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.

emissivity

(em-ă-siv -ă-tee) Symbol: ∊. A measure of a body's ability to radiate electromagnetic radiation as compared to that of a perfect radiator – a black body – at the same temperature.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

Emissivity

Ratio of radiation a surface gives off. Using products with low emissivity—for example, white roofs rather than black roofs—reduces the heat island effect, whereby urban landscapes become significantly warmer than surrounding rural landscapes.
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved

emissivity

[‚ē·mə′siv·əd·ē]
(thermodynamics)
The ratio of the radiation emitted by a surface to the radiation emitted by a perfect blackbody radiator at the same temperature. Also known as thermal emissivity.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

thermal emissivity

The ratio of the rate of radiant heat energy emitted by a body at a given temperature to the rate of radiant heat energy emitted by a blackbody, 1 at the same temperature, in the same surroundings.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
References in periodicals archive ?
16 is stating: The emissive power of an arbitrary cavity at thermal equilibrium is equal to the emissivity of the material which makes up the cavity multiplied by a function.
In both emissive OLEDs and transmissive LCDs, power consumption is relatively high because they either need a backlight or emit light.
This could be due to either electrons hopping into the conduction band of the Ti[O.sub.2] or the electrons tunnel through the emissive layer of the PFO without recombining with the holes or combination of both as illustrated in Figure 5(b).
For the emissive layers, which must be patterned, the company developed a nozzle printing process that simultaneously prints the red, green, and blue layers.
The layers are excited selectively, and the excitation wavebands for other primary colors pass through the top transparent layer(s) to address its emissive layer.
Here, an emissive layer is sandwiched between an n-type layer and a p-type layer, with the positive electrode connected to the p-type layer and the negative electrode connected to the n-type layer.
The device is ideal for measuring and ensuring the correct color of any product or graphic, and can measure reflective, transmissive and emissive color over large areas at one time.
Additional checks (penetrant testing, magnetic particle testing, ultrasonic testing) were made following the AE results (realized with the planar test configuration, with a 40 [dB.sub.AE] acquisition threshold), on a majority of the emissive regions.
The six sectors include lithium battery industry, organic light emitting diode (OLED) television or television having emissive electro luminescent screen thinner than LCD (liquid crystal display), shipbuilding industry, car component industry, electronic industry and motorcycle industry.
An organic EL display is a light emitting diode (LED) whose emissive electroluminescent layer is composed of a film of organic compounds.
Methods for polarimetric image formation, processing, and display are described, as are methods for modeling and simulation of both reflective and emissive polarimetric image formation of synthetic scenes.