Calcite , refractive index

Since the polarizers discussed above involve light reflection combined with the real part of the refractive index tensor, they can be used effectively over a broad spectral range about a central wavelength. Calcite Glan-Thompson polarizers, for example, operate successfully over the entire visible spectrum. When fabricated of crystalline quartz, these polarizers can be used to polarize ultraviolet light as well as visible light. 

Table 5.16. Calculated electric-dipole polarizability for COj " and refractive index n of calcite in sodium D light, for carbon-oxygen distance = 1.29 A...

Ghosh, G. (1999). Dispersion-equation coefficients for the refractive index and birefringence of calcite and quartz crystals. Out. Commun.. 163, 95-102. 

As molecular motion in a gas or liquid is free and random, the physieal properties of these fluids are the same no matter in what direetion they are measured. In other words, they are isotropic. True amorphous solids, beeause of the random arrangement of their constituent molecules, are also isotropic. Most crystals, however, are anisotropic, their mechanical, electrical, magnetic and optical properties can vary according to the direction in which they are measured. Crystals belonging to the cubic system are the exception to this rule their highly symmetrical internal arrangement renders them optically isotropic. Anisotropy is most readily detected by refractive index measurements, and the striking phenomenon of double refraction exhibited by a clear crystal of Iceland spar (calcite) is probably the best-known example. 

On the other hand, for example, calcite has a refractive index of 1.6, which is sufficiently different from most of the common plastics for some scattering and hence pigmentation to occur, but whiteness and opacity will only become very noticeable at high loadings and with thick products. 

The first observation of natural optical anisotropy was made in 1669 by Bartolinius in calcite crystals, in which light travels at different velocities depending on the direction of propagation relative to the crystal structure. The electrooptic effect, electric-field-induced anisotropy, was first observed in glass in 1875 by J. Kerr. Kerr found a nonlinear dependence of refractive index on applied electric field. The term Kerr effect is used to describe the quadratic electrooptic effect observed in isotropic materials. The linear electrooptic effect was first observed in quartz crystals in 1883 by W. Rontgen and A. Kundt. Pockels broadened the analysis of this relationship in quartz and other crystals, which led to the term Pockels effect to describe linear behavior. In the 1960s several developments... 

Figure 14.35, for example, shows the real (n) and imaginary (k) parts of the index of refraction (17 = n — ki) of three samples of dust collected in the Barbados, but thought to be transported from the Sahara Desert (Volz, 1973), from Afghanistan (Sokolik et al., 1993), and from Whitehill, Texas, in the southwestern United States (Patterson, 1981), respectively (Sokolik et al., 1998). Regions of absorption in the infrared due to some common dust components are also shown the asymmetric C-O stretch of carbonate in calcite near 7 gm seen in the Texas dust, the asymmetric Si-O-Si... 

Index of Refraction of Rock Salt, Sylvine, Calcite, fluorite, and Quartz 76 Ed. 

Plagioclase feldspar (Na-Ca aluminosilicate), other than albite, stains red potash feldspar (microcline or orthoclase) stains yellow, and quartz and glassy slag are unstained. Calcite takes on various shades of pink and dolomite may be deep red. The particles are normally examined in immersion mounts, utilizing liquids of known index of refraction and a cover glass. 

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