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Tantalum ores often contain significant amounts of niobium, which is itself a valuable metal.As such, both metals are extracted so that they may be sold. The overall process is one of hydrometallurgy and begins with a leaching step; in which the ore is treated with hydrofluoric acid and sulfuric acid to produce water-soluble hydrogen fluorides, such as the heptafluorotantalate.
Refraction at interface. Many materials have a well-characterized refractive index, but these indices often depend strongly upon the frequency of light, causing optical dispersion. Standard refractive index measurements are taken at the "yellow doublet" sodium D line, with a wavelength (λ) of 589 nanometers.
At temperatures approaching 450 °C the films produced have refractive indices and permittivity properties similar to those produced from conventional approaches. [12] The preparation of these films occurs with the loss of chloroethane: [12] Ta 2 (OC 2 H 5) 10 + Ta 2 Cl 10 → 2 Ta 2 O 5 + 10 C 2 H 5 Cl
A, B, and C depend on the band structure of the material. They are positive constants such that 4C − B 2 > 0. Finally, n(∞), a constant greater than unity, represents the value of n at E = ∞. The parameters B 0 and C 0 in the equation for n(E) are not independent parameters, but depend on A, B, C, and E g. They are given by:
The absolute refractive index n of an optical medium is defined as the ratio of the speed of light in vacuum, c = 299 792 458 m/s, ...
Molar refractivity, [1] [2], is a measure of the total polarizability of a mole of a substance.. For a perfect dielectric which is made of one type of molecule, the molar refractivity is proportional to the polarizability of a single molecule of the substance.
Compared to the constant speed of light in vacuum (c), the index of refraction of water is n = c/v. The Gladstone–Dale term ( n − 1) is the non-linear optical path length or time delay. Using Isaac Newton 's theory of light as a stream of particles refracted locally by (electric) forces acting between atoms, the optic path length is due to ...
The most general form of Cauchy's equation is = + + +,where n is the refractive index, λ is the wavelength, A, B, C, etc., are coefficients that can be determined for a material by fitting the equation to measured refractive indices at known wavelengths.