Polarized light is often used to extinguish specularly reflected light from smooth dielectric surfaces. For example, polaroid sunglasses are based on this principle. Polarization microscopy is widely used in a number of studies. A polarizing microscope is equipped with two polarizing prisms or two polaroids. One of them, the polarizer, is located in front of the condenser, and the second, the analyzer, is behind the objective. In recent years, special polarization compensators have been introduced into polarizing microscopes, which significantly increase sensitivity and contrast. With the help of microscopes with compensators, such small and non-contrast objects as intracellular birefringent structures and details of the structure of cell nuclei, which could not be detected by another method, were discovered and photographed. Polarizing filters are often used to enhance the contrast of transparent and low-contrast elements. For example, they are used when photographing a cloudy sky in order to enhance the contrast between clouds and a clear sky. The light scattered by the clouds is almost completely unpolarized, while the light from the clear blue sky is significantly polarized. The use of polarizing filters is the most effective means of enhancing contrast. Photoelastic analysis is of particular importance in technology. This is a method that allows you to judge mechanical stresses by phase displacement. To carry out photoelastic analysis, the part under study is made of a transparent material with a high coefficient of photoelasticity. The main part of the installation for photoanalysis is a polariscope, which consists of an illumination system, a polarizer, an analyzer and an eyepiece. If a flat glass strip is subjected to tension, then the glass will be somewhat deformed, mechanical stresses will arise in it. As a result, it will become birefringent and will shift the phase of the light wave. By measuring the phase shift, the voltage value can be determined. The method of photoelastic analysis can also be applied in ophthalmology, since photoelastic phenomena are detected in the membranes of the eye.
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