2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/89569Wheeler's delayed choice experiment, a well known manifestation of the complementarity principle, has proved somewhat difficult to physically interpret. We show that, restated in quantum field theoretic language, the experiment submits to a simple explanation: that wave- or particle-nature is imposed not at the slit plane but at the detector system. The intepretational difficulty conventionally encountered is due to the assumption of enforcement of complementarity at the former.3 pages; REVTeX; 3 new references added: Y.-H. Kim et al. (1995), D. Home (1994), J. Wheeler (1994); some changes to the Introduction; Version accepted in Current Science (2001)Quantum Physicstext