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

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.

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.

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.

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.
References in periodicals archive ?
1 can be expressed in terms of emissive power in the following form:
The three parties will also work to improve coating property of the phosphorescent polymer and prolong the device life, aiming to achieve a 150 lm/W emissive efficiency and a luminance half life of approximately 50,000 hours for white lighting by 2015.
It's just easier to read on a high contrast reflective surface than an emissive display.
And by 1995, the amount of our chlorine going into emissive uses will be under 5%.
Developers, manufacturers, graduate students, and engineers in display technology will find eleven chapters addressing the following topics: electronic addressing, CMOS backplane technology, transmission microdisplay structure, transmissive and reflective liquid crystal microdisplays, LCD assembly and testing, micromechanical devices, emissive microdisplays, projection displays, and near-to-eye systems.
While fluorescent organic EL devices are already available on the market for mobile phone display applications, phosphorescent organic EL devices, which are yet to be commercialized, can theoretically produce four times higher emissive efficiency, resulting in about one-fourth electricity consumption.
Type C fused quartz, flat panel, Type FB flat quartz infrared heaters, gas premix and catalytic panel heaters, UltraHigh intensity heaters, and Unitube tubular quartz infrared heaters provide peak efficiencies by matching emissive wavelengths of heating elements to absorption wavelengths of product (Selective Wavelength Method).
The new panel can reproduce blacker blacks and the details of dark images thanks to its new "Crystal Emissive Layer.
Of the total OLED materials market value, the active OLED materials - emissive materials, hosts, and hole/electron injection and transport materials are expected to account for nearly USD 3 billion.
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