I have a mental picture of photon scattering that goes like this: An atom spontaneously emits a single photon (or particle). Since the photon hasn't been observed, its wavefunction and probability expands out like a sphere. If I take my photodetector and place it at some point on this expanding sphere, I will detect this photon with probability 1/(4*Pi*radius). If I detect the photon, this collapses the wavefunction and I say the photon momentum was in the direction of my photodetector. If I don't detect the photon, but I know it was emitted, the photon is still traveling in a outward sphere. Or is the wavefunction now affected by my photodetector? Can anyone comment on this picture?