Originally Posted by wogoga in #46
Originally Posted by Ziggurat in #47
Ok. My reasoning with two phase-shifted radio signals (each divided into two sub-signals) is analogous to the 'one photon takes all paths
' hypothesis, and this (in my opinion untenable) hypothesis can indeed explain (at least lateral) coherence.
Nevertheless, your statement that a slit makes the superposed phase of photons (passing at the same time) "the only relevant phase
" isn't true either. Your conclusion "the slit becomes a coherent source
" (#39) logically depends primarily on the 'one photon takes all paths
' hypothesis, and not on blocking photons which are not in phase.
Two photons passing a slit can only be fully blocked if they have exactly opposite phase (e.g. one photon with phase 0
and the other with Pi
). In the case of a phase shift between two photons of phi = Pi/2
, the probability of passing the slit is Cos[phi/2]2
= 50% for each photon. So there is a 25% chance of both photons passing the slit. Because of their phase shift of Pi/2
, the two photons cannot interfere in the same way, as two coherent photons with phase shift 0
would do. Therefore the slit cannot cause incoherence to completely disappear.
By the way, no interference takes place between orthogonally polarized photons. From Wikipedia
: "Temporal (or longitudinal) coherence implies a polarized wave at a single frequency whose phase is correlated over a relatively great distance (the coherence length) along the beam.
So, for explaining that "the slit becomes a coherent source
", you need apart from "the superposed phase becomes the only relevant phase
" also something like "the superposed polarization becomes the only relevant polarization".