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Light scattering depends on, among other factors, particle shape and orientation in respect of the directions of the incident and scattered light. This complicates both the problem of calculation of light scattering, as well as determination of particle properties from light scattering data. Reasons for this complication include a significant increase in the complexity of light scattering models for particle shapes other than the sphere.
This prompted a long-lasting series of attempts to examine or justify the possibility of using simple particle shapes (such as spheres, spheroids, cylinders, etc.) in modeling of light scattering by irregular particles, such as dust. Some of the recent attempts are cited in Effective particle size as well as in Effective particle shape and the topics following the latter one. Representing actual shapes of irregular, randomly oriented particles by spheres, or better yet, by shape distributions of spheroids with a range of aspect ratios, has been demonstrated to work relatively well for the retrieval of the particle size from light scattering, (see Effective particle size and also Dubovik O et al 2006). However, it may produce rather poor results when the retrieval of an effective particle shape is attempted.
Random orientation of irregular particles has been frequently invoked as a justification for using simple shapes (e.g. sphere) to represent the actual particle shapes. However, random orientation cannot randomize the effects on light scattering of irregular particle shapes that are not identical to their mirror images of themselves, such as a spiral, or a fractal aggregate (Kolokolova L et al 2006), especially if circularly polarized light is considered. In fact, as shown by Guirado D et al (2007) from first principles, unpolarized light can become circularly polarized on scattering by dispersion of randomly oriented asymmetrical particles with no mirror forms of such particles.
| CITATION: Jonasz M. 2006. Effective particles in light scattering (www.tpdsci.com/Tpc/EfPt.php). In: Top. Part. Disp. Sci. (www.tpdsci.com). |
HISTORY: Published: 30-May-2006 Modified: 01-Oct-2007 Peer-reviewed: 21-Jun-2006 |
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