ABSTRACT
We meet a direct scattering problem if scatterer, embedding material, and incident field are known and the scattered field has to be calculated. In the sense of Huygens’ principle superimposing elementary waves-a point source synthesis-we have to move forward in time requiring the knowledge of Green functions of the embedding material. As a special problem the radiation interaction of the scatterer with itself arises rendering the direct scattering problem as a nonlinear problem with regard to the geometry of the scatterer. Therefore, linearizations such as the Born or Kirchhoff approximation neglect this radiation interaction.
