الفهرس 
Abstract
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Abstract
The electromagnetic (EM) scattering by objects is useful in many fields such as optics, geophysics, engineering, medicine, and biology. The objects may represent dust, aerosols, cloud, and biological cells. Studying the scattering of EM waves by such objects provides information of these particles (i.e. size, shape, number of scatterers,…etc). For example, understanding the scattering and absorption properties of cloud particles help to investigate the climate changes. In addition, the appearance of many physical phenomena as halo arcs, rainbows, and coronas, actually represents concentrations of reflected, refracted, or diffracted natural light in the scattering phase functions of atmospheric particles of various shapes, sizes, and orientations. In most of these applications, the shapes of the particles are complicated and aggregated in clusters. Finding light-scattering properties for such clusters is a challenging task.
The main aim of this thesis is to study the scattering of a plane wave or a focused laser beam by a cluster of different particles. To the best of our knowledge, no attempts are published in the literature to tackle such type of problems. This problem can be divided into two parts; the first is the incident beam modeling, and the second is the interaction of the incident beam with the cluster. In this study, the angular spectrum of plane waves is used to model any incident shaped beam. Then the modified cluster T-matrix method is used to calculate the scattered fields. This combination of the plane wave spectrum technique and the modified cluster T-matrix method is a powerful technique to calculate the scattered field intensities of a cluster composed of different spherical and nonspherical particles illuminated with any incident EM fields.
A technique of the T-matrix superposition method (SM) for computing the scattered fields of a plane wave or shaped focused beam by a cluster consisting of complicated morphology microparticles is developed and presented in this work. The T-matrix superposition method was previously presented for a cluster of spherical components for which the individual constituent’s matrix is diagonal. In this thesis, we modified the cluster T-matrix to be suitable for a cluster consistsing of nonspherical, and homogeneous or layered particles for the individual matrix is a full matrix. The angular scattering intensities (in a fixed orientation) and the scattering matrix elements (in a random orientation) of two distinctly types of clusters; chain, and packed clusters, illuminated with a plane wave or a focused laser Gaussian beam are computed. Also the scattered fields of such clusters but consisting of coated spherical, coated spheroidal particles, nonconcentric coated axisymmetric particles are analyzed. Moreover clusters consisting of different axisymmetric shaped particles illuminated with a plane wave or a focused Gaussian beam are studied.
As a last part of this thesis the developed technique is applied to real life applications such as clusters of normal and abnormal red blood cells (RBCs) and white blood cells (WBCs). The computed angular scattering and the elements of the complete scattering matrices as funtions of the scattering angle of a cluster composed from normal and abnormal blood cells are compared with those of a cluster of normal biconcave RBCs. Also the effects of increasing white blood cells (WBCs) in a blood sample are demonstrated.