As far as the art of conversation, several here are lacking. The only thing I conceed to Brizonbiovizier is that the word physical could have been in inverted commas but in actuality the reaction would be as physical as anthing is physical. You will see the post is addressed to owl37400 and Tenson and this should give you its relevence. If you are not interested in an open discusion don't post. If it pleases you to highlight others lack of understanding then that is unfortunate. It would be better of you to try and explain something if it is clear to you that they do not understand a concept. If I say the experiment involved a very low power light source (resulting in no wave type interaction) then that is what I mean, do not presume to tell me I am mistaken. With regards the question I asked myself, you have come to the other conclusion, which is fair enough.