2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/85184The standard zone plate assumes that the shortest ray connecting a radiation source and a detection point has a phase of 0 deg thereby defining a reference phase. Here we examine the experimental consequences of varying this reference phase from 0 deg to 360 deg. It is concluded that reference phase is an intrinsic and useful property of zone plates.16 pages, 7 figuresOpticsGeneral Physicstext