The Foldy–Lax approximation is valid for nearly resonating frequencies

The waves (including acoustic, electromagnetic and elastic ones) propagating in the presence of a cluster inhomogeneities undergo multiple interactions between them. When these have sub-wavelength sizes, dominating field due to is Foldy–Lax field. This models equivalent point-like scatterers, located at centers small inhomogeneities, with scattering coefficients related geometrical/material properties each as polarization coefficients. One questions left open for long time whether we can reconstruct this from scattered measured far away inhomogeneities. would allow us see (or detect) approximation paradigm). In work, show that indeed valid soon enjoy critical scales their sizes contrasts. These them generate resonances which be characterized computed. main result here exciting by incident frequencies are close real parts allows collected itself (as farfields). short, using nearly resonating frequencies. demonstrated using, dielectric nanoparticles 2D TM model bubbles 3D acoustic waves.