Figure 5.4 — The scattering problem Figure 5.4 — The scattering problem. Pictorial view of a scattering process. Scattering theory studies how an incoming electromagnetic wave is scattered by a particle. In general, when light impinges on an object, the object emits a scattered electromagnetic field, which in the far field is a spherical wave. In particular, given an incoming linearly polarised plane electromagnetic wave (Ei) in a medium of refractive index nm impinging on a particle of homogeneous refractive index np, one wants to determine the electromagnetic field inside the particle (Ep) and the scattered electromagnetic field (Es), both in the near field and in the far field.