Reflected light optical microscopic

Figure 7.1. Schematic of the components of (a) transmitted light optical microscope and (b) reflected light optical microscope.

Isotropic materials have properties which are independent of the direction of examination, X-, y- or z-direction. As such, they appear with a purple color in the polarized light optical microscope and this color does not change on rotation of the stage of the microscope. Thus, reflectance and bireflectance are not relevant properties for isotropic carbons. The porous, isotropic carbons are easily identifled and distinguished from anisotropic carbons by this technique. 

Optical microscopy is another method that has been used to determine the distribution of minerals in coal. This method is based on the detailed microscopic examination of polished or thin sections of coal in transmitted and/or reflected light. In principle, observing several of its optical properties, such as morphology, reflectance, refractive index, and anisotropy, makes identification of a mineral type possible. 

Microstructures of the two siliconized silicon carbide materials, (a) SiC-C and (b) SiC-S, observed with reflected light under an optical microscope, showing different reflective indexes between Si (light) and SiC (dark). 

These needle-like plates are easy to separate from the substrate and also easy they to be mechanically split into more subtitle long objects. With an optical microscope, it is observed that the tip of these objects can reflect the incident light and expand it into a spectrum. 

A block-scheme of this apparatus is presented in Fig. 2.12, A and B. Compared to that given in Fig. 2.11, an adequate improvement is the use of fibre optic cable which conducts the light from Hg-Xe arc lamp to the reflected light microscope. The thickness is determined by the microinterferometric technique of Scheludko-Exerowa (see Section 2.1). 

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