Methods and apparatus for separating of parts from workpieces is provided, in which at least one part is separated from a workpiece by means of radiation, in particular by means of laser radiation, and in which the radiation acts on the workpiece in a zone of interaction in such a way that regions of the workpiece are abraded, changed in their shape and/or are separated; in which the light intensity is received from the interaction zone and/or its vicinity and is transformed into electrical signals by a photoelectric sensor, and in which, with use of the electrical signals, it is determined when the processing procedure is to be terminated.