Abstract: A method for activating photoinitiators in photosensitive substrates (6) like for instance printing inks, lacquers, and glue which set by radiation with UV light, and in which the photosensitive substrate and a light unit are moved relative to each other at a predetermined rate, the light unit comprising a UV light source (4) placed in a lamp housing (1) with a reflector (2, 10) for directing the UV light towards the substrate through an outlet opening, and in which the light emission is controlled by means of a control unit (50) emitting a signal to an electronic ballast (30) for the UV light source (4) depending on the mutual travel speed between the light unit and the substrate (6) and other predetermined parameters.

Abstract: A method for control of vegetation at places where said vegetation is undesirable, said method comprising intense irradiation of the vegetation for one or several periods by light, of which at least 10% of the effect is ultra-violet light, the total irradiation dosage (joule/m.sup.2) exceeding a minimal value necessary for the intended vegetation control. An apparatus for performing the method comprises at least one light source directed towards the undesired vegetation and emitting at least 10% of its light discharge in the ultra-violet range, said apparatus comprising means which after discharge of an irradiation dosage surpassing the minimal value necessary for the intended vegetation control discontinue the treatment of the areas in question.