how material absorbs or reflects light

[Brenda Melano 3H]

I am confused about how we see the colors of objects. We have always been told that an object absorbs light and reflects light and that the light it reflects is the light we see. Is the light it reflects the energy that the electrons absorb and then re-emits? If so, what happens to the energy of the photons that the material "absorbs"?

[Chem_Mod]

The interaction of everyday materials with light is a complicated concept due to the fact that any given material is a compound of different elements. Any discussion here would be a simplification of the process and must be taken with a grain of salt.

The color of materials owes to their electron orbital energy levels as one would expect. However, each electron orbital are occupied based on the principles of quantum mechanics. Without going too much into the details, every electron orbital can be occupied or unoccupied. As we know, transitioning from one orbital to another absorbs/emits light. These transitions occur for a number of reasons due to quantum effects but it is suffice to say that certain transitions occur, while others do not, while others occur very often or very quickly. It is these types of transitions that we get the color of objects, where light is initially absorbed promoting an electron into a higher "excited" energy level but is re-emitted due to instabilities owing to quantum mechanics and the electron "relaxes" to a lower energy level.

Light that was absorbed and not emitted are usually used in some other processes, i.e. changes in molecular structures (like in transition lenses), thermal relaxation (object gets hot), decomposition of molecules (photo-bleaching), etc.

[Lisa Leung 2H]

Then would it be correct to say that the reason heated metal objects glow red or white is because of the transition of electrons? But why don't we see heated objects glowing green when the transitions occur and light is emitted?

[Chem_Mod]

Heating an object usually only access the nearest energy level, say n=1 to n=2. Most objects that are heated by conventional methods get around ~500K or so which, using the Wien's displacement equation from the blackbody radiation section, corresponds to radio frequencies. You would have to heat things up to ~5000 K to start getting colors like yellow or orange (which is about the temperature of the sun). Of course, these are blackbody systems which are ideal systems. For metals and such, one can get green or blue if you heat them up to ~3000 K which is why fireworks are blue, green, etc.