2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/94714We note that Einstein's relativistic Doppler formula presents a strange aspect. For incident light received under a fixed non zero angle, the Doppler shift will change from blueshift to redshift (or vice-versa) for some critical relative velocity of the observer and the source.2 pagesClassical PhysicsGeneral Physicstext