ABSTRACT
How is it possible that entities with distinct wave properties, i.e. having considerable spread in space and governed by the superposition principle, in some situations behave just like particles? One possible answer, suggested by Schrödinger, is that the real entities must be wave packets of such a minute dimension that they sometimes act as point-like particles. For example, if the effective extension of the wave packet is less than the size of a film grain in a film emulsion, then each wave packet will most often hit only one film grain and we would observe singular dots on the film, i.e. we observe such a particle-like behaviour.
