2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/21537We analyze refraction of electromagnetic wave packets on passing from an isotropic positive to an isotropic negative refractive index medium. We definitively show that in all cases the energy is always refracted negatively. For localized wave packets, the group refraction is also always negative.5 pages, 3 figuresCondensed Mattertext