Visibility light extinction

Regional Haze Visibility Impairment any humanly perceptible change in visibility (light extinction, visual range, contrast, coloration) from that which would have existed under natural conditions, caused predominantly by a combination of many sources from, and occurring over, a wide geographic area. 

Upon irradiation with a monochromatic visible light, extinction of the silver nanoparticles deposited on a... 

This facile reaction involves a modest change in the absorption of visible light, largely because of the visible absorption band of <7 -azobenzene [1080-16-6] having a larger extinction coefficient than azobenzene [17082-12-1]. Several studies have examined the physical property changes that occur upon photolysis of polymeric systems in which the azobenzene stmcture is part of the polymer backbone (17). 

Natural Conditions conditions substantially unaltered by humans or human activities, as applied in the context of visibility, natural conditions include naturally occurring phenomena that reduce visibility as measured in terms of light extinction, visual range, contrast, or coloration. 

Figure 6. Difference extinction spectra of the silver nanoparticles on the rutile XiO2(100) single crystal after irradiation with monochromatic visible light (wavelength = 480 nm, light intensity 5.0mW cm , irradiation time = 30 min 550 nm, 5.0mW cm , 30min 600nm, 3.0mWcm , 60min (FWHM = lOmn)).

Silver nanoparticles can be deposited on Ti02 by UV-irradiation. Deposition of polydisperse silver particles is a key to multicolor photochromism. The nanoparticles with different size have different resonant wavelength. Upon irradiation with a monochromatic visible light, only the resonant particle is excited and photoelectrochemically dissolved, giving rise to a decrease in the extinction at around the excitation wavelength. This spectral change is the essence of the multicolor photochromism. The present photoelectrochemical deposition/dissolution processes can be applied to reversible control of the particle size. 

The depth-profile of photon absorption is analogous to that for UV-visible light, i.e. I = Io exp(-Ad), where the mass energy absorption coefficient, u/g is used instead of the extinction coefficient. Particulate energy absorption can be described by relative stopping powers. 

Light extinction coefficients per unit mass of chemical constituent are constant for growing aerosols for certain forms of the growth laws and particle size distributions. Constant coefficients simplify source allocation analyses for visibility degradat ion. 

The long-term average total extinction coefficient at downtown Los Angeles is 6.62 10 m (19) as inferred from daytime measurements of gjevailing visibility. Elemental carbon present at about 9 pgm with a specific absorption of 11.9 m g would account for about 17% of total light extinction at downtown Los Angeles. 

Figure 11.6 The effect of size dispersion on extinction of visible light by water droplets. Each curve is labeled with a, the standard deviation in the Gaussian size distribution.

Absorption of visible light with high molar extinction coefficient (e) of over thousand. 

Osmium(II) and ruthenium(II) complexes are strongly absorbing species. Their extinction coefficients are in the range (5—11) x 103 M-1 cm-1 around 500 nm. The corresponding complexes in the oxidation state 3+ absorb visible light much weaker and therefore the GO-catalyzed oxidation of D-glucose by Os111 complexes, which obeys stoichiometric Eq. (43), can be monitored spectrophotometrically as in the case of ferricenium salts. 

Dyes such as erythrosin B [172], eosin [173-177], rose bengal [178,179], rhodamines [180-185], cresyl violet [186-191], thionine [192], chlorophyll a and b [193-198], chlorophyllin [197,199], anthracene-9-carboxylate [200,201], perylene [202,203] 8-hydroxyquinoline [204], porphyrins [205], phthalocyanines [206,207], transition metal cyanides [208,209], Ru(bpy)32+ and its analogs [83,170,210-218], cyanines [169,219-226], squaraines [55,227-230], and phe-nylfluorone [231] which have high extinction coefficients in the visible, are often employed to extend the photoresponse of the semiconductor in photoelectro-chemical systems. Visible light sensitization of platinized Ti02 photocatalyst by surface-coated polymers derivatized with ruthenium tris(bipyridyl) complex has also been attempted [232,233]. Because the singlet excited state of these dyes is short lived it becomes essential to adsorb them on the semiconductor surface with... 

Applications of visible light such as the use of polarized light, birefringence, retardation, angles of extinction, dispersion staining, and phase contrast will be explained, discussed and related primarily to asbestos with some discussion of quartz. 

Figure 19.6. Light Absorption By Chlorophyll A. Chlorophyll a absorbs visible light efficiently as judged by the extinction coefficients near 10 M i cm f... 

One of the most widely recognized aspects of atmospheric pollution is reduced visibility, which is due primarily to light extinction by particles. A common measure of visibility is visual range (F/ ), which is defined as the maximum distance at which a black object can be seen against the horizon, as follows ... 

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