What is it exactly about a surface that makes it reflect or absorb some or all wavelengths of light?
Forgive me if I am being thick, but could you explain point 2. more? What is it about the phonon modes? For instance, if a surface just reflects a particular colour, is that because the phonon vibrates at the same frequency as that colour? If so, how does that stop the light from being absorbed?1. the presence of conduction electrons
2. the nature of the phonon modes in the material