Following the failure of classical physics theories to explain the interference patterns observed in double slit experiments and other light diffraction experiments and because of the similarities between these patterns and the interference patterns generated by waves at the surface of a liquid, physicists deduced that light was behaving as a wave which led to the so-called wave-particle duality of light. Since the particle model could explain phenomena such as the photoelectric effect and since the wave model of light described the interference patterns of light, it made sense to deduce that light had to corpuscular or wave-like depending on the experiment performed on it. But what experiments actually showed is that neither accepted models of light could explain both behaviours and emphasized the need for a new theory.
Note: The chapter below is from Quantum-Geometry Dynamics; an axiomatic approach to physics Quantum-Geometry Dynamics; an axiomatic approach to physics. All units are discrete fundamental units as derived in the book.
