2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/88882Application of the uncertainty principle to conditional measurements is investigated, and found to be valid for measurements on separated sub-systems. In light of this, an apparent violation of the uncertainty principle obtained by Kim and Shih in their realization of Popper's experiment (quant-ph/9905039) is explained through analogy with a simple optical system.7 pages, 2 figuresQuantum Physicstext