What determines whether a surface reflects or absorbs light?

[Sea Cow]

What is it exactly about a surface that makes it reflect or absorb some or all wavelengths of light?

 

[ZapperZ]

What is it exactly about a surface that makes it reflect or absorb some or all wavelengths of light?

1. the presence of conduction electrons
2. the nature of the phonon modes in the material

Zz.

 

[Andy Resnick]

Alternatively, the index of refraction.

 

[Sea Cow]

1. the presence of conduction electrons
2. the nature of the phonon modes in the material

Zz.

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?

Thankyou for your patience.