Light scattering

Diane Gurniak


Scattering arises from inhomogeneities within the medium in which an electromagnetic wave is propagating. This paper deals with both the theory of scattering and its applications as a means of exploring the temporal and spatial characterstics of media on a microscopic scale. The theoretical discussion of scattering demonstrates the existence of scattering and its induction by dielectric variations throughout a medium. It also develops a correlation function containing the microscopic information that determines the nature of the scattered light and extends the development from a time independent function to a time dependent one. This theory is then applied to the experimental determination of the size of microscopic particles. An experimental method for collecting the necessary data is presented and several methods of analysis are discussed. This apparatus used in conducting the experiments reported on in this paper is also presented along with the results of a study of the performance of this apparatus and the experimental errors inherent in it. Finally, scattering from samples of distilled water, tap water and suspended sediment was measured and it was found that the distilled water contained scatterers 1.55 and 2.5 micrometer in diameter, the tap water contained scatterers 1.33 and 0.044 micormeter in diameter. The existence of diffractive effects is also shown for particles larger that a wavelength in size.