Wave and photon descriptions of light: historical highlights, epistemological aspects and teaching practices

The wave and the photon descriptions of light are discussed in connection with interference and the Doppler effect. Both phenomena can be described in terms of waves or in terms of photons. However, the two descriptions are not equivalent. While the photon description deals with a single photon, the wave one deals with the behaviour of many (enough) photons. The wave description’s predictions are in agreement with experiment only when the high number of photons used (one at a time or all together) overshadows their spatially localised interaction with the detectors. These arguments are dealt with on the basis of historical breakthroughs in the light epistemological considerations and teaching implementations.