Refraction, light definition

The refractive index is a function of the frequency of the light, and it normally decreases with increasing wavelength, as illustrated in Figure 6.90 for some typical glasses. The variation in refractive index with wavelength, A, is called dispersion, and it is given in one definition by... 

The flame is not, however, a discontinuity. There are definite gradients of temperature and composition because of conduction of heat and diffusion of reaction products into the fresh gas. The temperature gradients have been studied by three techniques direct measurement with very fine thermocouples (24, 25, 43) refraction of a narrow slit of light (11, 16) and tracing the path of a stroboscopically lighted dust particle and computing temperature from its direction and velocity (l, 27). 

The depth of penetration plays a critical role in the definition of the optical volume that is being sampled. It depends on several parameters, above all on the wavelength of the incident beam, on the angle of incidence, and on the refractive indices of the two media. This consideration is important in sensing applications in which the interaction of a chemical species with this field gives rise to an analytical signal. For common materials and for visible light, dp is typically between 100 and 200 nm. 

One of the most important parameters in static LLS is the specific refractive index increment (dn/dC), defined as Zzmc o(dn/9C)T,p,A- Since this parameter is not an intrinsic property of the polymer, the conditions of fixing temperature T, pressure P and wavelength of light in vacuum X are needed in its definition. Note that, according to Eq. (2.1), an error of E% in dn/dC will lead to an error of 2E% in the derived Mw. 

Figure 5.8 The bending (refraction) of a light ray on passing from a less dense medium (air) into a more dense medium (oil), and definitions of the angles of incidence (/) and refraction (r).

The electromagnetic wave theory of light enables the definition of the molar refractivity... 

Refractive index — A fundamental physical property of materials through which light can travel. It is usually indicated by the symbol n, and it is defined as n = c/cQ, where c0 is the speed of light in vacuum and c corresponds to the speed at which the crests of electromagnetic radiation corresponding to a specific frequency propagate in a material [i,ii], A more rigorous definition for the refractive index of a dense and isotropic material composed of a unique kind of particles (atoms or... 

For mirrors, the equation is usually written 1/s + 1/s = 2/R = 1/f. A diverging mirror is convex to the incoming light, with negative f. From this fact we conclude that R is also negative. This form of the equation is consistent with that of the lens equation, and the interpretation of sign of focal length is the same also. But violence is done to the definition of R we used above, for refraction. 

In a photochromie system all of the refractive-index change is a result of photoinduced reactions of isolated molecules, and there is no mass transport over distances larger than molecular dimensions. Since each molecule functions independently, the spatial frequency response of photochromic systems extends from zero to the diffraction limit of the recording light. (This is frequently referred to as "molecular resolution.") While our definition of a photochromic system does not require that the process be reversible, many photochromic systems are reversible, optically and/or thermally (31). In fact, it is in general only with photochromic processes that one can obtain, reversible image recording. 

It follows from the above definition, that x is the angle between the stream lines and the optic axis in the flowing liquid — this axis being so defined as to be always between 45° and 0°, relative to the stream lines. The refractive index for light vibrating with electric... 

If we ignore the small effect of two-phonon transitions on the dispersion of the refraction index n, then in the region of the energies E = hu>, corresponding to the excitation of two-particle states, the absorption coefficient n is found to be directly associated with the density of two-particle states. In fact, for light polarized, for instance, along the x-axis, which coincides, by definition, with the direction of the vector dBB, the dielectric tensor has a nonvanishing component... 

The turbid liquids which were thus obtained were found to possess not only the usual properties of liquids (such as the property of flowing and of assuming a perfectly spherical shape when suspended in a liquid of the same density), but also those properties which had hitherto been observed only in the case of solid crystalline substances, viz. the property of double refraction and of giving interference colours when examined by polarised light the turbid liquids are anisotropic. To such liquids, the optical properties of which were discovered by 0. Lehmann, the name liquid crystals, or crystalline liquids, was given." Since the term crystal implies the existence of a definite space lattice, which is not found in the case of liquid crystals, it is perhaps better to use the term anisotropic liquids, ... 

The optical purity is usually, but not always, equal to enantiomer excess. In order for the two to be equal, it is necessary that there be no aggregation. It is possible, for example, that a homochiral or heterochiral dimer (see Glossary, Section 1.6, for definitions) would refract the circularly polarized light differently than the monomer (or each other). In 1968 [19] Krow and Hill showed that the specific rotation of (S)-2-ethyl-2-methylsuccinic acid (85% ee) varies markedly with concentration, and even changes from levorotatory to dextrorotatory upon dilution. In 1969 [20], Horeau followed up on Krow and Hill s observation, and showed that the optical purity (at constant concentration) and enantiomer excess of (5)-2-ethyl-2-methylsuccinic acid were unequal except when enantiomerically pure or completely racemic. This deviation from linearity is known as the Horeau effect, and its possible occurence should be remembered when determining enantiomeric purity by polarimetry. 

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