::Another demonstration that that is not the explanation: if you close one slit, eliminating the interference pattern, the intensity of light (number of bullets) reaching the screen will decrease in some areas and increase in others.  This is the proof that the light waves from the two slits are interacting.  If it was only "bullets" bouncing off the edges of the slits, closing one slit could only decrease the number of bullets reaching a given area of screen, not increase it.