2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/90087Reflection of a normal incident matter wave by a perfectly reflecting wall moving with a constant velocity is investigated. A surprising phenomenon is found-that if the the wall moves faster than the phase velocity of the incident wave, both the reflected and incident waves propagate in the same direction. This counter-intuitive result is an example which shows that common sense is not always credible when one deals with quantum problems.2 pages revtex fileQuantum Physicstext