Scattering from Spheres: A New Look into an Old Problem

In this work, we introduce a theoretical framework to describe the scattering from spheres. In our proposed framework, the total field in the outer medium is decomposed in terms of inward and outward electromagnetic fields, rather than in terms of incident and scattered fields, as in the classical Lorenz-Mie formulation. The fields are expressed as series of spherical harmonics, whose combination weights can be interpreted as reflection and transmission coefficients, which provides an intuitive understanding of the propagation and scattering phenomena. Our formulation extends the previously proposed theory of non-uniform transmission lines by introducing an expression for impedance transfer, which yields a closed-form solution for the fields inside and outside the sphere. The power transmitted in and scattered by the sphere can be also evaluated with a simple closed-form expression and related with the modulus of the reflection coefficient. We showed that our method is fully consistent with the classical Mie scattering theory. We also showed that our method can provide an intuitive physical interpretation of electromagnetic scattering in terms of impedance matching and resonances, and that it is especially useful for the case of inward traveling spherical waves generated by sources surrounding the scatterer.

Automated summary

The study introduces a theoretical framework for describing scattering from spheres, which decomposes the total field in terms of inward and outward electromagnetic fields and provides intuitive understanding of reflection and transmission coefficients. It extends previous theories by introducing impedance transfer expression and yields closed-form solutions for the fields inside and outside the sphere, allowing for evaluation of transmitted power and connection with the modulus of the reflection coefficient. The method is consistent with classical Mie scattering theory and offers intuitive physical interpretation of electromagnetic scattering, especially for inward traveling spherical waves.