Reflection and absorption

Attenuation of radiation as it passes through the sample leads to a transmittance of less than 1. As described, equation 10.1 does not distinguish between the different ways in which the attenuation of radiation occurs. Besides absorption by the analyte, several additional phenomena contribute to the net attenuation of radiation, including reflection and absorption by the sample container, absorption by components of the sample matrix other than the analyte, and the scattering of radiation. To compensate for this loss of the electromagnetic radiation s power, we use a method blank (Figure 10.20b). The radiation s power exiting from the method blank is taken to be Pq. 

Optoelectronics is a discipline which combines optics and electronics. It deals with optical wavelengths from 0.20 im (ultraviolet) to 3 im (near infrared) as shown in Fig. 15.1. The properties of optoelectronic materials are a useful combination of electrical and semiconductor properties (electron action), with optical properties such as transmission, reflection, and absorption (phonon action). 

Because of the role these algae play in the oceans biological productivity and their impacts on climate due to the removal of carbon dioxide, satellite sensors have been employed to measure the chlorophyll a contents in oceans, lakes, and seas to indicate the distribution and abundance of biomass production in these water bodies. Detection is set at the specific reflectance and absorption wavelengths of the light from the upper layer of the ocean where photosynthesis occurs. 

Nacreous and Interference Pigments. The optical principles of nacreous (interference) pigments are shown in Figure 72 for a simplified case of nearly normal incidence without multiple reflection and absorption. At the interface P, between two materials with refractive indices n t and n2, part of the beam of light L, is reflected (L,) and partially transmitted (i.e., refracted) (L2). The intensity ratios depend on n, and n2. In a multilayer arrangement, as found in pearl or pearlescent and iridescent materials (Fig. 71 C), each interface produces partial reflection. After penetration through several layers, depending on the size and difference between n1 and n2,... 

It is well known that the frequency of an oscillator shifts or "pulls" when the reflection and absorption of its load changes. In commercial and military applications, this trait is detrimental and is prevented. By measuring this frequency shift however, the characteristics of the load can be extremely accurately determined. Specifications indicate that this technique is 100 times more sensitive to process variable changes than other types of measurement systems, with accuracies to 1% and for some applications to. 01%. 

Response times of undoped and Co-doped crystals for an incident intensity of 1 W/cm2 and a grating spacing of 0.7 pm are shown in Table 1. No systematic trend is apparent from these data, at least partially due to experimental uncertainties such as sample heating and variable reflection and absorption losses. Response times of as-grown and reduced Fe-, Mn-, and Cr-doped BaTi03 (18) range from 200 to 1200 ms under the same experimental conditions. Thus, it is clear that response times can vary considerably for crystals with different dopants and oxidation states. Additional experiments are needed to achieve better control over this key property. 

Because the sample must be placed in a cell (sample container), there is an interaction between the radiation and the cell walls, which produces a loss of power at each interface as a result of reflections and absorptions. In order to prevent or minimize these effects, the power of the transmitted beam is usually compared with the same radiation beam that passes through a reference cell containing only the solvent. Therefore, the measured absorbance is defined by the equation A = log (AoiveiAampie) = log (/(//), where /solvent and /sample are the intensities of the beams emerging from the solvent and sample cell, respectively. 

Pennington and co-workers developed equations for prediction of the total heat gain through a double glazed window with drapes as a function of the transmissivity, reflectivity, and absorptivity of individual barriers, amounts of direct and diffuse solar... 

Because a measurement under a defined atmosphere requires that the sample be placed in a cell, corrections for both the optical components (of the spectrometer and the accessory) and the reflection and absorption by the window(s) become necessary. 

Pande et al. 2009 (44) MWCNT CVD As-synthesized Solvent casting CNT Loading level 10 vol.% Two- step method loading levels CNT 10 vol.% Film Bulk Composites EMI SE in X-Band Layered composite (7 layers of 0.3 mm thickness film) - 40 dB Bulk composite (2 layers of 1.1 mm thickness bulk specimen) 30 dB Contribution of SEA and SEK to SEThuiI was studied SE dominated by absorption Stacking method results in increased multiple reflections and absorptions for layered composite ... 

Fig. 14. Polarized reflectance and absorption spectra of single-crystal Ba[Pt(CN)4) 4 H20 (295 K, 1 bar). The fi c polarized reflectance spectra and the corresponding calculated absorption spectra are taken from Ref. 136, the Elc polarized ones from Ref. 135, 138. The high energy structures in the reflectance spectra are enlarged by a factor of 10 (use left hand scale)...

The polarization of the exciton spectra of ZnO does not follow the classical model. All the three exciton series are strongly polarized and can be observed only with E L c (A, B) and E c (C). This has led to contradictory position schemes of the two highest valence bands (Tg, Ty) and values of Aso, Acr. There are also certain discrepancies in the results of different papers on the nature of the lines of complex discrete reflectivity and absorption spectra of ZnO at 4.2 K, as well as on the bands and excitons parameters. " ... 

The transmission, reflection and absorption of the solar radiation may finally be calculated by the formulae ... 

The UV-vis reflection and absorption spectra of the clathrochelate [Cu(thiopenar)] (0104)2 complex made it possible to establish that the copper(II) polyhedron both in solution and in the solid state has a distorted square-pyramidal structure [206],... 

A common inconsistency is the coordinate use of acid and basic. It would seem that the first term should be acidic if the second is basic. Another example is the use of reflectometer and absorptiometer. As the process terms are reflection and absorption, it seems that the names of the instruments should be spelled consistently. Reflectometer has long been used. Absorptometer (or absorptimeter) is the obvious, consistent term. 

Fig. 4 Schematic diagram showing the nature of reflection and absorption from (A) low loss dielectric, (B) metallic, (C) monolithic high loss dielectric, and (D) a composite or particulate ceramic with high dielectric loss. (From Sutton, W.H. Microwave processing of ceramic materials. Am. Ceram. Soc. Bull. 1989, 68, 376-386, Fig. 2, page 377. Reprinted with permission of The American Ceramic Society, www.ceramics.org. Copyright 1989. All rights reserved.)...

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