A method for calculating the electromagnetic scattering for the truncation of the multipolar expansions describproperties of a cluster of spheres of arbitrary radii and ing the scattered field. The convergence of the expan-(possibly complex) refractive indexes is proposed. The sions is tested through the application to the simple but approach takes proper account of multiple scattering significant system of two spheres with varying interpareffects and does not require any approwinlation except ticle separation.

We propose to study the scattering properties of dense distributions of spherical scatterers by resorting to an iterative solution of the Foldy-Twersky equation for the propagation of the coherent field. As a result of the first step of the iterative procedure, the host medium is substituted by an effective medium of complex refractive index to account for the multiple-scattering processes that occur among the particles. Although we truncate the above-mentioned iterative procedure to the second step, the results of our calculations are in excellent agreement with previous experimental results of Zaccanti et al. ("Measurement of optical properties of high-density media," to be published in Applied Optics) for the scattering coefficient of Intralipid solutions up to a volume density of 15% and show a limited disagreement at a volume density of 22%.

A method for studying the scattering properties of a cluster of dielectric spheres is proposed. The vector scattering problem is handled through Debye potentials and a mathematical technique that accounts for multiple scattering effects. The scattered field as well as the scattering and absorption cross sections can be computed without any restriction of principle on the angle of incidence of light and on the radia and refractive indexes of the spheres in the cluster. The resulting expressions take on the well known form when the cluster reduces to a single sphere.

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