*(Its, or associated. That is somehow the question).
I can think of, at least in principle, a perfectly reflecting optical cavity with dimension comparable to the wavelength of the electromagnetic wave associated to a photon. Say, a kind of internally reflecting sphere with diameter of a wavelength or smaller (or a comparable cube etc for that is matter).
Would be possible for that photon to exist inside that object?
How this relates to the "size of a photon", where now size stands for the spread of the probability to find it (sort of "De Broglie wave for a photon") and what would change in this respect if the photon won't be confined?
I ended up to this while thinking about the meaning of the various jiggling arrows we draw when depicting photons arriving at a place, motivated by the common widespread feeling of getting lost when asked what it really means. In other words by thinking of a wave that, tough interacting as a point particle, must conveys information about an oscillating em field. It seems it needs at least a wavelength (in that medium) to do so. I hope that the question above is more clear than the motivation that drove me to write it.