[SOLVED] Wave/Particle Duality in Light Quanta All right. It's a really simple concept to state, but a really difficult one to grasp. I'm curious about a specific experiment, if someone could explain it to me. The one slit/two slit experiment. With a constant stream of light and one razor-thin slit, we see an illuminated circle on a wall. With two slits, we see alternating bars of light and dark, the light ones decreasing in intensity as they extend toward the periphery. This is not what I am curious about. What I want to know is why, when a single photon is fired through the single slit (call it Slit One), it can land on a spot where, during the first experiment, there would be a black bar, (we can track it using a photographic plate), but if we open up Slit Two and fire the photon through Slit One the photon lands elsewhere. The information I have regarding the phenomenon is slightly outdated, so I was wondering if there was a new theory.