Geometric optics applicability

FIGURE 6.3 Absorption of light of a highly divergent beam by a substance placed in a cylindrical cell. Although the effect of reflection on the window has not been considered here, it can be introduced by a simple application of the laws of geometrical optics. 

For very large particles, i.e. a 1 or Dp > 4-A., the laws of geometrical optics (also called the Fraunhofer regime) are applicable (van de Hulst 1981). The light scattering intensity varies approximately with the square of the particle diameter. 

A quantitative study of the role played by the laser wavefront curvature and other geometrical/optical parameters on the transmitted far-field intensity profile [3] demonstration of self-defocusing effect for optical limiting application [4]. 

By this technique both the particle diameter and the average distances of separation of the randomly spaced particles can be determined. Using particles ranging from 10 to 50,000 nm in diameter, Dragsdore (160) showed that for smaller particles a diffraction theory was applicable, whereas with large ones, th e geometric optics of a refraction and reflection theory was more useful. 

Discrepancies between these results arise for droplets with a diameter of 51 /Xm and an ink concentration of 25 per cent. It ensues from the application of the f-d-relation according to the geometrical optics approach, i.e. the assumption that only one light scattering component exists. However -d-relation predicted by Mie theory is not linear any more. 

Ring substituted phthalocyanines are mixtures of geometrical isomers [68], unless they are structurally made to be symmetrical, such as octa-substituted phthalocyanines [69,70. The synthesis of pure, un-symmetrical phthalocyanines have been reported. For example, Konami and Hatano [71] reported the isolation of mono-t-butyl zinc phthalocyanine, which is soluble in organic solvents, by a chromatographic technique. Leznoflf and Hall [72] showed that unsym-metrical phthalocyanines can be synthesized by a polymer support method. Numerous investigators showed that mono substituted phthalocyanines can be synthesized by reacting a substituted 1,3-diiminoisoin-dolenine with a chlorosubphthalocyanine [73]. The synthesis of these compounds is usually quite elaborate and these compounds are primarily targeted to molecular electro-optical applications. 

Uniform and Gaussian beams 10-2 Light containment by a fiber 10-3 Applicability of geometric optics... 

The reduction of dimensions also reduces volumes which are accessible to the detector. Thus, detection principles related to geometric dimensions of the detector cell ai e not ideally suited for coupling to microsystems, whereas surface sensitive principles, such as electrochemical methods or optical methods utilizing the evanescent field of a waveguide, or methods which can be focussed on a small amount of liquid, such as electrochemiluminescence (ECE), ai e better suited. This is why electrochemiluminescence detectors ai e combined to microsystems. Moreover ECE has found wide applications in biochemistry because of its high sensitivity, relatively simplicity and feasibility under mild conditions. 

TayW43 Taylor, W. J. Applications of Polya s Theorem to optical, geometrical and structural isomerism. J. Chem. Phys. 11 (1943) 532. 

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