opacity

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opacity

1. the state or quality of being opaque
2. an opaque object or substance
3. Physics Photog the ratio of the intensity of light incident on a medium, such as a photographic film, to that transmitted through the medium
4. Logic Philosophy the property of being an opaque context

opacity

(oh-pass -ă-tee) A measure of the ability of a gaseous, solid, or liquid body to absorb radiation. It is the ratio of the total radiant energy received by the body to the total energy transmitted through it. For gaseous material of a particular chemical composition, opacity depends on both temperature and density. Various processes contribute to the opacity: energy absorption by electrons bound to an atom or ion, allowing them to jump to a higher level or to escape from the atom as free electrons (bound-bound or bound-free absorption); absorption by free electrons (free-free absorption); scattering of photone of radiation by free electrons or atoms (Compton scattering); absorption of γ-ray photons by ambient ‘gas' photons (photon-photon absorption). The negative hydrogen ion, H, is a particularly important source of opacity in a star like the Sun, and the solar opacity is seen to drop rapidly to zero at the Sun's limb.

Opacity

Quality of being impenetrable by light; not reflecting light, or transmitting light, neither transparent nor translucent.

opacity

[ō′pas·əd·ē]
(optics)
The light flux incident upon a medium divided by the light flux transmitted by it.

opacity

The quality of being opaque, as the capacity of a paint to cover or obliterate a background over which it is applied.

opacity

Being "opaque," which prevents light from shining through. For example, in an image editing program, the opacity level for some function might range from completely transparent (0) to completely opaque (100).
References in periodicals archive ?
The main clinical characteristics of the MIH are: de- marcated opacities, posteruptive breakdown and atypical restorations.
Treating the MIH has some challenges such as sensitivity, increased risk of plaque accumulation, unexpectedly rapid development and progression of caries, inability to anaesthetize, pulpal inflammation (due to the porosity of the enamel), difficult cooperation of the young patient (dental fear and anxiety), severe discomfort, repeated marginal breakdown of dental restorations and unpredictable behavior of apparently intact opacities.
Clinical characteristics of MIH are: demarcated opacities (altered enamel translucency, variable in degree) of different colour, post-eruption break- down, atypical restorations, and extracted first permanent molars due to MIH.
We use atmospheric opacities at 880 nm derived from ground-based measurements of the Pancam instrument onboard the Mars Exploration Rovers (Lemmon et al.
This is mainly caused by higher opacities at this site (Figure 1, top and middle), which are partly affected by the aphelion cloud belt.
Radiative opacities for carbon- and oxygen-rich mixtures.
Rosseland mean opacities for variable compositions.
New solar opacities, abundances, helioseismology, and neutrino fluxes.
In some cases you may need to view the opacities with the illumination in two positions.
Patients with cortical opacities can also report monocular diplopia and this should always be considered in an older patient with symptoms of diplopia.
The development of enamel opacities implies that ameloblasts are affected during the enamel maturation stage.
18 ppm) and prevalence of diffuse opacities in the permanent first molars and incisors among children is low as well (0.