A monochromatic, coherent light source is targetted through a pair of double slits, and produces a series of small dots on a background screen. According to Young, this is caused by the interference of light wave trains, constructively and destructively interfering to produce antinodes and nodes respectively. This is one argument used to establish light to have a wave-like nature. Yet when the experiment is repeated in a different manner, this time to slow down the intensity of the photons so that each passes through the slit, one at a time, this also produces the same interference pattern. Yet this is explained by a "probablity function". Why doesn't this latter experiment simply disprove this wave-like nature of light suggested by Thomas Young in this particular instance?