A light source emits a weak beam of low frequency (I will explain later why low frequency) light, so that a revelator "ticks" once every, let's say, minute. Sometimes in physics books or in scientifical magazines, it's explained this way: "one single photon is emitted from the source every minute, travels to the revelator and it's revealed". Question: How can we say that, in this case, a spatially localized particle travels from the source to the revelator? A way to prove it would be to put...another revelator in the middle of the route, so destroing the photon (here is why low frequency and hence low energy); so we are left with the same question: What is the photon from the source to this new revelator? What could the photon be if not the "click" of the revelator?