>>16685204
You can shoot the electrons one at a time, they will still accumulate in a wave pattern. The first weird think you notice is when you cover one of the slits. The dark fringes and interference pattern disappears. So, by covering one of the fringes, the electron can reach places it couldn't before (those regions of destructive interference) . When you open the slit, the dark fringes reappear. You'd expect the opposite to happen. If you allow the electron more paths to travel trough, you'd expect it to reach more places, not less. But that's not what happens.