I have tried to find a cause-effect answer to why a mirror works. I understand that a photon interacting with a metal surface will cause a collective excitation of the conduction electrons called a surface plasmon but I haven't found any explanation why the reflection law is obeyed when the photon is reemitted. Please dont' answer any crap about the conservation of momentum. That is a calulation rule, not an explanation. Too often confused in physics education. Any ideas?