Relationship to refractive index

Water Content and Refractive Index. The water content of a hydrophilic contact lens is a determinant of other properties. The relationship of water content and Dk is discussed above. Water content in lenses is inversely related to refractive index (23), a key property for vision correction. A lens material with a higher refractive index refracts light to a greater degree, allowing more vision correction with a thinner material. The water content of a lens is generally determined gravimetricaHy or inferred from the relationship to refractive index, measured with a refractometer (24). 

Since a is not easily determined, use is made of its relationship to refractive index, n, according to the equation... 

Published refractive index data for the mobile phase, polystyrene, polyacrylonitrile, and the two monomers were used to calculate refractive index detector calibrations for the two homopolymers. The published data were used to determine relationship between refractive index increments of monomer and corresponding homopolymer. Chromatographic refractometer calibrations for the two homopelymers were then calculated from experimentally measured calibration data for the two monomers. 

In regard to Equation (5.4), we have to note that without the above mentioned assumptions the nonlinearities will contain weighting factors that are proportional to the corresponding wave-vector mismatch and inversely proportional to refractive index, thus suggesting that the THG signal is sensitive to the refractive index interface(s) as well. In order to differentiate between contrast mechanisms in THG imaging of soft tissue materials it would be important to know the relationships of the corresponding linear and nonlinear optical parameters. A nonlinear optical... 

Table 21.9 Relationship of refractive index to Brix for high-fructose syrups60...

Before considering ways to change the refractive index of a material, it is useful to review the relationship between refractive index and various other physical and chemical characteristics. 

Refractive Index. The refractive index of fats and oils is an important characteristic because of the ease and speed with which it can be determined precisely, the small amount of sample required, and its relationship to structure. It is useful for source oil identification, for observing progress of reactions rapidly, and for establishing purity. The general relationship between refractive index and the composition of an oil product with minor exceptions are as follows (104) ... 

If the orientation of the principal optical directions can be found with respect to the unit cell vectors of the crystal, the orientations of the molecules in the unit cell, especially those with very anisotropic shapes and considerable unsaturation, may be found. This information was useful in the determination of the shape and size of the steroid nucleus (see Figure 1.11, Chapter 1). The relationship of molecular shape to refractive index is listed in Table 5.2, and the different refractive indices of naphthalene are shown in Figure 5.11. 

The refractive index (RI) is a parameter that relates to molecular weight, fatty acid chain length, degree of unsaturation, and degree of conjugation. A mathematical relationship between refractive index and iodine value (IV) has been described by Perkins (1995b) as... 

As shown above, there is a well-defined relationship between refractive index and electric susceptibility. According to Eq. (4.24), the refractive index is a measure of the degree of induced polarization in a given medium. We have to admit, however, in the case of an anisotropic medium that the derivation of the relationship between refractive index, dielectric constant, and permeability is very complex and a nuisance because eri and / n are tensors, and the refractive index is different for each direction of the propagated light. 

Refractive index values have been used to identify drugs, including sulphanilamides, for example at their melting point436 or in acetone solution437. Rapaport and Solyanik438 found a linear relationship of refractive index and concentration in NaOH or HC1 solutions which they utilized for quantitative determination. 

The relationship between refractive index and the atomic or molecular structure of a material was considered in Sections 11.1.4 and 11.1.5. Recall that light can be treated as a varying electric field and this interacts with the internal charges on the solid. At the frequency of a light wave, only the electrons respond, and so contribute to the refractive... 

Indicatrix n. A three-dimensional construction of the optical relationships in the crystal. Radii proportional in length to refractive index values or velocities may be used to represent principal index directions of the crystal. 

For polarized measurements the relationship between refractive index and absorbance is critical. Directional absorbance changes lead to birefringence, which in turn will affect strongly the nature of polarized light. The Kramers-Rronig relations come into play for cases like this one (15). They relate the complete electromagnetic absorption spectrum of a material to its refractive index at all frequencies and vice versa. A form of the relation is... 

Is ambiguous (Figure 10)12 he value of the Sl/N atomic ratio, determined from XPS measurements is found to obey a linear relationship with refractive index and thus it is possible to express the fraction of NH bonds as a function of the stoichiometry of the film (Figure 11). It can be seen from this relationship that it is possible to tune the amorphous silicon nitride to the required refractive index, e.g. for optical waveguide applications, within the range 1.6 to 2.1. 

Sellmeier Equation An empirical relationship between refractive index and wavelength for a particular transparent medium. The equation is used to determine the dispersion of light in the medium. It was first proposed in 1871 hy W. Selhneier, and was a development of the work of Augustin Cauchy on Cauchy s equation for modeling dispersion. 

Reciprocal relationship between the hydrodynamic radius of multicomponent precursors as a function of root aging time at 50°C and pH 3 and corresponding refractive indices of films prepared from the multicomponent borosilicate precursors after different aging times. The strong mutual screening of branched polymeric precursors leads to a reciprocal relationship between polymer size and pore volume (inversely related to refractive index). From Drinker et al. [20J. 

Solvents exert their influence on organic reactions through a complicated mixture of all possible types of noncovalent interactions. Chemists have tried to unravel this entanglement and, ideally, want to assess the relative importance of all interactions separately. In a typical approach, a property of a reaction (e.g. its rate or selectivity) is measured in a laige number of different solvents. All these solvents have unique characteristics, quantified by their physical properties (i.e. refractive index, dielectric constant) or empirical parameters (e.g. ET(30)-value, AN). Linear correlations between a reaction property and one or more of these solvent properties (Linear Free Energy Relationships - LFER) reveal which noncovalent interactions are of major importance. The major drawback of this approach lies in the fact that the solvent parameters are often not independent. Alternatively, theoretical models and computer simulations can provide valuable information. Both methods have been applied successfully in studies of the solvent effects on Diels-Alder reactions. 

It is important to note that comparable information to that obtained from infra-red spectroscopy can in principle be obtained from refractive index measurements. It has been shown that for a transversely isotropic film, the relationship equivalent to 11(c) is... 

Using the ideal gas law and the relationship (n — 1) oc p between refractive index n and density p leads us to the refractive index structure function. 

By deriving or computing the Maxwell equation in the frame of a cylindrical geometry, it is possible to determine the modal structure for any refractive index shape. In this paragraph we are going to give a more intuitive model to determine the number of modes to be propagated. The refractive index profile allows to determine w and the numerical aperture NA = sin (3), as dehned in equation 2. The near held (hber output) and far field (diffracted beam) are related by a Fourier transform relationship Far field = TF(Near field). 

The polarisability, a, of the molecule is proportional to the refractive index increment dn/dc, and to the relative molar mass of the molecule in question. The full relationship is ... 

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