2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/115012It is proved that one can choose a control function on an arbitrary small open subset of the boundary of an obstacle so that the total radiation from this obstacle for a fixed direction of the incident plane wave and for a fixed wave number will be as small as one wishes. The obstacle is called "invisible" in this case.Mathematical Physics35J05, 35R30, 74J20, 74J25text