Whats the difference between reflection and scattering of photon? (QFT)

[enroger0]

Just read Feynmen's QFT and been wondering the difference between photon reflection by a perfect mirror and photon scatter by say a rough surface.

In both cases, photons are said to be absorbed by electrons and re-emitted.

But in reflection case, photons get to "preserve" its wave information (wavefunction never collapse, phase increase by pi/2). I think in QFT, photons are said to have virtual interaction with all the electrons on the mirror?

In scattering case, photon is absorbed by a specific electron and re-emitted, destroying all wave information.

So what decide photon when to be reflected when to be scattered?

Thanks for the help, just a curious laymen here.

 

[azntoon]

The difference between photon reflection and photon scattering is determined by the type of surface that the photons interact with. If the surface is perfectly smooth and reflective, then the photons will be reflected, preserving their wave information. If the surface is rough or non-continuous (i.e. made up of many smaller particles, such as a sandpaper-like material), then the photons will be scattered in multiple directions, losing all of their wave information in the process.