As far as I can tell we have only ever seen photons. It is thus an experimental beast par excellence. No-one has ever seen a photon wave, only the effect of individual photons. Call me greedy, but both would be good. So much for expectations.
L is doomed to end in divorce.
Irreconcilable differences, as they say. I have to say that that is the answer I expected at the start from the luminaries in this group. I was mildly astonished to find it unforthcoming. Equally I expected someone to say that my variable-leg length interferometer would merely move the entire diffraction pattern left and right as I altered one leglength, but that was not forthcoming. I strongly feel that one should be able to devise an experiment that will give you differing results depending on the differences in wavetrainlength.