how empty (or filled) is the empty (matter) wave? The de broglie-bohm interpretation posits that: in a single particle double slit experiment, the photon goes through one of the slits/paths and the matter waves go through both the slits. the path without the photon and just the matter wave has, for convenience, been labelled as empty wave. Also it is generally imagined that the empty wave has no energy or momentum. why is that so? however does this not contradict with some of the below observations: - the empty wave (travelling the other path) effects the behaviour/path of the photon. Is not some form of energy required to effect the path of the photon? - the empty wave is blocked by opaque obstacles however it passes through transparent obstacles. if it was just a probability wave, why would it get effected by an opaque object but not a transparent object. the matter wave passes through the same obstacles that a photon would pass through and gets blocked by the same obstacles that a photon would get blocked by. therefore its properties are similar to that of a photon off track question (and I have asked this before but the response was weak): Does the matter wave of a photon interact with the matter wave of an electron? the above, i guess, must be easy to test experimentally.