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We deal with the electromagnetic waves propagation in the harmonic regime. Wederive the Foldy-Lax approximation of the scattered fields generated by acluster of small conductive inhomogeneities arbitrarily distributed in abounded domain $\Omega$ of $\mathbb{R}^3$.  This approximation is valid under a sufficient but general condition on thenumber of such inhomogeneities $m$, their maximum radii $\epsilon$ and theminimum distances between them $\delta$, the form $$(\lnm)^{\frac{1}{3}}\frac{\epsilon}{\delta} \leq C,$$ where $C$ is a constantdepending only on the Lipschitz characters of the scaled inhomogeneities. Inaddition, we provide explicit error estimates of this approximation in terms ofaforementioned parameters, $m, \epsilon, \delta$ but also the used frequencies$k$ under the Rayleigh regime. Both the far-fields and the near-fields (statedat a distance $\delta$ to the cluster) are estimated. In particular, for amoderate number of small inhomogeneities $m$, the derived expansions are validin the mesoscale regime where $\delta \sim \epsilon$.  At the mathematical analysis level and based on integral equation methods, weprove a priori estimates of the densities in the $L^{2,Div}_t$ spaces insteadof the usual $L^2$ spaces (which are not enough). A key point in such a proofis a derivation of a particular Helmholtz type decomposition of the densities.Those estimates allow to obtain the needed qualitative as well as quantitativeestimates while refining the approximation. Finally, to prove the invertibilityof the Foldy-Lax linear algebraic system, we reduce the coercivity inequalityto the one related to the scalar Helmholtz model. As this linear algebraicsystem comes from the boundary conditions, such a reduction is notstraightforward.

The Foldy-Lax Approximation for the Full Electromagnetic Scattering by Small Conductive Bodies of Arbitrary Shapes