I would have thought we could say a photon approaches the screen? It is one packet of em energy.
Don't we only ever "see" em waves as photons or discrete packets of energy...We don't get two halfs of a photon showing up. It is only when they transfer energy that they become visible everything in-between is a mathematical model. we could emit one photon at a time with a break - thats a series of photons isn't it?