Does a photon have a 3-D envelope of a certain size? (Assume a photon travelling in free space, and by 'envelope', I mean some space outside of which the field strength of the photon's electromagnetic fields drops below some threshold, say 1% of maximum.) If so, how big is the envelope? Does the size vary with some other property of the photon, like wavelength? Related question: Do multiple oscillations of the fields exist within one photon at any moment, spread over space? If so, how many within the envelope?