Wavelength-dependent transmittance

FIGURE 6.19 Wavelength-dependent transmittance of a 130-nm-thick ITO film on an acrylic-layer-coated PET substrate. 

Transient transmittance of single-walled carbon nanotubes (SWNTs) in suspension was modulated at two periods of T40 and 21 fs, corresponding to the RBM and G mode, respectively [54,55]. The amplitude and the frequency of the coherent RBMs exhibited a clear excitation-wavelength dependence (Fig. 2.15) [54]. The different frequencies were attributed to SWNTs with different diameters coming to the excitonic resonance. The FT spectra of the coherent RBMs in Fig. 2.15 had noticeable differences from the resonant Raman spectra, such as the different intensities and better frequency resolution. 

Kylling, A., A. Albold, and G. Seckmeyer, Transmittance of a Cloud Is Wavelength-Dependent in the UV-Range Physical Interpretation, Geophys. Res. Lett., 24, 397-400(1997). 

Photometric accuracy is determined by comparing the difference between the measured absorbance of the reference standard materials and the established standard value. Many solid and liquid standards are commonly used to verify the photometric accuracy of a spectrophotometer. An optically neutral material with little wavelength dependency for its transmittance/absorbance is desirable because it eliminates the spectral bandwidth dependency of measurements. The advantages and disadvantages of various commonly used photometric accuracy standards are summarized in Table 10.6. Even for a relatively stable reference standard, the intrinsic optical properties may change over time. Recertification at regular intervals is required to ensure that the certified values of the standards are meaningful and accurate for the intended use. 

From the physical point of view, this method shows some problems (1) cos Z should be applied exclusively to direct irradiance (2) the transmittance terms should be applied only to direct irradiance (3) W0 and Fa are wavelength dependent. 

The films contained between 0.1 and 1% residual monomer according to gas chromatographic analysis. The transmittance and fluorescence spectra were measured with a Spectronic 505 spectrophotometer by Bausch and Lomb. To obtain correct fluorescence spectra with respect to energy, the above mentioned apparatus was calibrated using a wolfram-band lamp and an aperture driven by a wavelength-dependent correction... 

K4Nb60i7 crystals exhibit optical birefringence [34] and absorb in the UV region with an optical absorption edge between 320 and 330 nm. Figure 4 shows the wavelength dependences of the transmittance and absorption coefficient along the... 

The wavelength-dependent focal length and diffraction efficiency of diffractive lenses with a continuous profile are given, through transmittance diffraction analysis, by... 

The transmittance is T=sin (r/2). In the voltage-off state, the retardation is zero and the transmittance is zero for any wavelength. The retardation of the voltage activated states is wavelength-dependent and therefore the voltages for R, G, and B light to reach the maximum transmittance are different. 

Figure 8.2 depicts the normalized light transmittance TV) of the 90° TN cell at three primary wavelengths R = 650, G = 550, and B = 450 nm. Since the human eye is most sensitive at green, we normally optimize the cell design at i = 550 nm. From Equation (8.4), the first 71 = 1 occurs at dAn 480 nm. The color dispersion (i.e. the wavelength dependency of the light transmittance) at = 0 is not too sensitive to dAnIX beyond the first minimum. Therefore, the TN cell can be treated as an achromatic half-wave plate. The response time depends on the cell gap and... 

The value of s (the absorbance of a 1 M solution in a 1 cm cell) depends upon the nature of the absorbing species and on the wavelength of the incident radiation. Absorbance is thus seen to be directly proportional both to the concentration of the absorbing species and to the thickness of the absorbing medium. It is related to transmittance T defined as I/I0 (the fraction of radiation transmitted) by the equation... 

Elemental composition P 43.64%, 0 56.36%. The pentoxide is dissolved in water and the ultimate hydrolysis product, H3PO4, is analyzed for PO4 by ion chromatography. Alternatively, the solution is treated with ammonium molybdate—ammonium vanadate reagent to produce a yellow colored vanado-molybdophosphoric acid. Absorbance or transmittance of the solution may be measured at a wavelength between 400 to 490 nm, depending on. concentration of P04. The solution must be diluted for analysis. The solution may further be reduced with stannous chloride to form an intensely colored molybdenum blue for measuring absorbance or transmittance at 690nm. 

Many techniques are based on this principle and can be used for the analysis of all types of samples. The spectrum obtained from reflected light is not identical to that obtained by transmittance. The spectral composition of the reflected beam depends on the variation of the refractive index of the compound with wavelength. This can lead to specular reflection, diffuse reflection or attenuated total reflection. Each device is designed to favour only one of the above. The recorded spectrum must be corrected using computer software. 

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