Relative index of refraction

ErO Energy flux due to thermal i Relative index of refraction... 

In terms of the relative index of refraction, n — 2/ i) < 1, the following expressions follow from SnellS law for angles of incidence greater than the critical angle ... 

Figure 6. Dependence of the extinction coefficient and relative index of refraction of low MMA oligomers on the degree of polymerization.

As was mentioned, when the fluid phase is a liquid, we do not expect the radiation heat transfer to be significant, although there are exceptions for some high-temperature applications. However, in Table 9.5, the index of refraction of some liquids is given for the sake of completeness. In treatment of scattering from particles, the relative index of refraction, that is, njnf, is the significant parameter, and as expected when dealing with liquids, this ratio can be substantially different from ns. 

Sometimes the relative index of refraction or relative refractive index, denoted n, is used and corresponds to the dimensionless ratio of the absolute index of refraction of a substance to that of a reference substance, usually air. Because the index of refraction of air is close to unity, the two quantities are often confused ... 

Dmin minimum particle diameter to be measured (fim) ni index of refraction of external medium U2 index of refraction of particle Orel relative index of refraction, ni/n2... 

For particles in a two-phase system, a relative index of refraction is used. This is defined as the ratio of the velocity of light in the suspending medium, to the velocity in a particle, Vy. 

Titanium metal is considered to be physiologically inert. When pure, titanium dioxide is relatively clear and has an extremely high index of refraction with an optical dispersion higher than diamond. 

Kaolinite and dickite are easily distinguished where they occur in recognizable crystals (87). Nacrite is relatively rare. HaUoysite (7 E) is usually exceedingly fine-grained, showing a mean index of refraction of about 1.546. The index of refraction for haHoysite (10 E) varies somewhat with the immersion Hquid used it ranges from 1.540 to 1.552 (83). 

Measuring the index of refraction of a material is generally done using an instrument known as a refractometer. Typical values of the index of refraction of gemstones and other materials are listed in Table 19. The relatively high index of refraction of diamond, for example, accounts for its distinct brilliance and multicolor display the index of refraction of rutile, a gemstone composed of titanium dioxide, is even higher than that of diamond, and rutile is indeed more brilliant than diamond. 

Water absorption can also cause significant changes in the permittivity and must be considered when describing dielectric behavior. Water, with a dielectric constant of 78 at 25°C, can easily impact the dielectric properties at relatively low absorptions owing to the dipolar polarizability contribution. However, the electronic polarizability is actually lower than solid state polymers. The index of refraction at 25°C for pure water is 1.33, which, applying Maxwell s relationship, yields a dielectric constant of 1.76. Therefore, water absorption may actually act to decrease the dielectric constant at optical frequencies. This is an area that will be explored with future experiments involving water absorption and index measurements. 

In general, measuring beads requires less laser power than measuring cells because of their higher index of refraction (n 1.5 for polystyrene beads vs. n 1.37 for cells).15 The optical force imparted to a particle scales with the difference in index of refraction between the particle and the fluidic medium.16 For bead measurements, we typically operate at a laser power of 2.5 W, whereas for cell measurements the laser is operated at 10 W to obtain similar displacements. These relative power levels are in line with the comparative refractive index differences between the two different particle types and water. 

The KTP chips are individually immersed in a molten bath of a mixture of RbNOs and Ba(N03)2. Within this bath, the Rb ions diffuse into the unmasked portions of the KTP chip, while the K ions diffuse out of the substrate and into the bath, shown in the illustration in figure 6. In the diffused regions, the rubidium ions increase the index of refraction relative to the undiffused KTP and thus form the optical waveguide. Note that due to the presence of barium, there is an increase in the index of refraction and the ferroelectric domain in the diffused region is reversed and hence the term chemical poling is used for this process. 

The naturally occurring dioxide exists in three crystal forms anatase, rutile and brookite. While rutile, the most common form, has an octahedral structure. Anatase and brookite have very distorted octahedra of oxygen atoms surrounding each titanium atom. In such distorted octahedral structures, two oxygen atoms are relatively closer to titanium than the other four oxygen atoms. Anatase is more stable than the rutile form by about 8 to 12 kJ/mol (Cotton, F.A., Wilkinson, G., Murillo, C.A and M Bochmann. 1999. Advanced Inorganic Chemistry, 6 ed, p. 697, New York John Wiley Sons) Other physical properties are density 4.23g/cm3 Mohs hardness 5.8 g/cm ( anatase and brookite) and 6.2 g/cm ( rutile) index of refraction 2.488 (anatase), 2.583 (brookite) and 2.609 (rutile) melts at 1,843°C insoluble in water and dilute acids soluble in concentrated acids. 

This scheme of frequency tripling was successfully tested with fuchsin in hexafluorisopropanol (a solvent selected for its low index of refraction and relatively flat dispersion curve) to frequency-triple the output of a neodymium laser 67,68) With an input power of 10 MW/cm2 a third-harmonic output of 0.2 mW/cm2 was measured. This low value was mainly due to the relatively high absorption of fuchsin at 355 nm. An improvement of the efficiency by a factor of 80 was found with hexamethylindocarbocyanine iodide in hexafluorisopropanol because of the much lower absorption of this dye at 355 nm. Since the absorption minimum of this dye is at 383 nm, one could expect an additional efficiency increase by a factor of 70 for a fundamental laser wavelength of 1.15 / 69>. Other cyanine dyes have been used for frequency tripling a fundamental wavelength of 1.89 /mi 70>. 

Note that the index of refraction of the continuous phase and that of the dispersed particles enter the evaluation of the various efficiencies. The light that actually strikes the particles is used in the determination of x- This light differs from that under vacuum by the refractive index of the medium. This effect enters the calculation of the x values in that it is the ratio of the refractive index of the particle relative to that of the medium that determines the extinction. 

Carbon-fluorine bonds also have unusual electrooptical properties. Fluoropolymers are often used to provide favorable electrical properties such as low dielectric constants. The low dielectric constants are another consequence of the relatively low polarizability of C—F bonds. Polarizability a is related to index of refraction n through the following equation ... 

The absolute index for all ordinary transparent substances is greater than 1 (see Table 1) but there are some special cases (X-rays and light in metal films, which are discussed below) for which the index of refraction is less than unity. Since the absolute index for air exceeds unity by less than 0.0003, the relative indices for solids and liquids in air are very nearly equal to their absolute indices. It should be noted that since the refractive mdex vanes with the wavelength, any exact statement of its value must specify the wavelength to which it refers in Tables it is usually given for sodium light of frequency 5.893A. See also Dispersion. 

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