2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/203300If a homogeneous plane light-like shell collides head-on with a homogeneous plane electromagnetic shock wave having a step-function profile then no backscattered gravitational waves are produced. We demonstrate, by explicit calculation, that if the matter is accompanied by a homogeneous plane electromagnetic shock wave with a step-function profile then backscattered gravitational waves appear after the collision.Latex file, 15 pages, accepted for publication in Physical Review DGeneral Relativity and Quantum Cosmologytext