Polarizing prism

Magnesium fluoride occurs in nature as the mineral, sellaite. It is used in glass and ceramics. Single crystals are used for polarizing prisms and lenses. 

Let us suppose that we place a polarizing prism between the light source and the sample. If the sample is a single crystal in which all of the molecules have the same orientation relative to the crystallographic axes, we can so orient the crystal that the direction of the electric vector of the light will correspond to the x, y, or z direction in a coordinate system for the molecule. It is then possible that some transition may occur for only one or two of these orientations but not for all three. 

An equally accurate measurement of the phase difference is obtained when a quarter wave plate is introduced between rotor unit and analyzer in the usual way (extinguished between the crossed polarizing prisms). As is well-known, this quarter wave plate transforms the ellipticity of the light-wave emerged from the rotor unit into a rotation according to the simple relation ... 

As to the practical way of producing a suitable modulation, a series of proposals have been made. In practically all cases a modulator is introducted into the light beam, whereas the polarizing prisms are kept at rest. It appears that the general shape of the lower curve in Fig. 6.5 remains unchanged. More precise calculations can be carried out with the aid of a matrix calculus, as reviewed by Walker (216). 

Table 6.1. Values oj phase differences caused by windows and polarizing prisms...

Date of measurement windows taken together Polarizing prisms taken together... 

It is seen that the absolute values of the apparent phase differences of the polarizing prisms are actually somewhat larger than those of the windows. The signs of the phase differences are irrelevant for the present qualitative description. They depend on the mutual orientations of the parasitic effects. 

The just described compensation method for the parasitic birefringence of windows and polarizing prisms is also useful with respect to the parasitic birefringence created by reflections from the cylinder walls. As has been pointed out, the disturbance caused by the windows is compensated at its maximum. This means, as the test fluid possesses an extinction angle of 45°, that the extinction positions of the window birefringence are oriented parallel and perpendicular to the direction of flow (i.e. the... 

Figure 2. Cotton s experimental apparatus for measuring absorption coefficients for left-and right-circularly polarized light. p1 incoherent source Lj, L2, focusing lenses Nj, N2, Nicol polarizing prisms M2, limiting apertures Fj, F2, quarter-wave Fresnel rhombs S, sample cell p2, location for light detection (visual). From ref. [2].

Figure 13. Experimental arrangement for time-resolved CD measurements of photolysis transients based on an ellipticity measurement. FL, flashlamp Lj, L2, L3, L4, collimating/focusing lenses F, interference filter PH, Pv, Glan-Thorapson polarizing prisms oriented orthogonally to each other SP, strain plate S, sample cell. From ref. [39].

Figure 5 shows the polarized spectra of myristamide, with the subscripts indicating orientation of the a or 5 crystal axis with the polarization direction of the polarizing prism. In Fig. 6, AT Fi corresponds to the strong-...

The principle of the method using the elliptical compensator is based on Eq. (106) expressing intensity I of the light passing through crossed polarizing prisms P and A and two thin anisotropic plates placed between these prisms at azimuths t) and tjk with respect to the polarizer P and introducing the phase differences 5 and 6 respectively )... 

Crossed Nicol prisms An arrangement of two materials (calcite polarizing prisms or Polaroid discs) such that the first, the polarizer, transmits plane-polarized light that passes through the second, the analyzer, only if oriented in specific ways. 

Use Ceramics, glass, single crystals for polarizing prisms, lenses and windows. 

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