On the other side of the slits, each separated piece of the wave function, one from the left and one from the right slit, spreads out again and both form sets of mathematical ripples that overlap, at some points reinforcing and at other points canceling each other’s amplitude. The combined effect is that the wave function now has the pattern characteristic of other wave phenomena, such as light. But bear in mind that this now complicated wave function is still describing only a single atom.
