2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/129321We show that the mode corresponding to the point of essential spectrum of the electromagnetic scattering operator is a vector-valued distribution representing the square root of the three-dimensional Dirac's delta function. An explicit expression for this singular mode in terms of the Weyl sequence is provided and analyzed. An essential resonance thus leads to a perfect localization (confinement) of the electromagnetic field, which in practice, however, may result in complete absorption.14 pages, no figuresClassical PhysicsGeneral Physicstext