The phenomena may be analysed in several appropriate ways. The incoming and outgoing diffracted objects may be treated severally as particles or as waves. The diffracting object may be treated as a macroscopic classical object free of quantum features, or it may be treated as a physical object with essentially quantum character. Several cases of these forms of analysis, of which there are eight, have been considered. For example, Schrödinger proposed a purely wave account of the Compton effect.