On interference: the scalar problem

Single-slit and two-slit interferometer measurements of electrons are analyzed within the realistic model of particle propagation. In a step by step procedure we show that all current models of interference are essentially non-local and demonstrate that the treatment of the quantum theory of motion is the simplest model for the scalar problem. In particular we give a novel interpretation of the quantum potential Q, which should be regarded as a non-classical and essentially statistical term describing the changes of the quantum ensemble due to a change of the physical environment.