# About light interacting with matter

Is it possible to predict the color of a solid object based on its molecular formula?

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It is, if you can detail how the molecule/molecular formula will absorb/retransmit incoming photons.

Al

But what about the influence of neighboring molecules - don't they also affect the energy levels of a given electron? It seems so complicated. How does one even begin?

But what about the influence of neighboring molecules - don't they also affect the energy levels of a given electron? It seems so complicated. How does one even begin?

Exactly. It is very difficult. As far as i know, our knowledge of said phenomenon at this point is more analytic than synthetic (i.e. our models, if present arent very good and an experiment would have to be conducted to see what actually happened).

Hmm.. I've always wondered about this question. Why is this red book red? this purple shirt purple? etc.

At the end of the first chapter of A Brief History of Time, Stephen Hawking says,

"...the partial theories that we already have are sufficient to make accurate predictions in all but the most extreme situations,"

so I've assumed that there's a way - at least in principle - to say, the formulae for the kind of molecules the make up this paint are so-and-so, therefore the paint is green. But I've never looked into the matter far enough to get anywhere. I know how it works with gases where the molecules are practically isolated from one another and the electron energy levels are discrete, but with solids I've never had a clear idea.

alxm
I know how it works with gases where the molecules are practically isolated from one another and the electron energy levels are discrete, but with solids I've never had a clear idea.

Well, if you have an atom with two states, and add another atom with two states (and they interact), you end up with four states (you can view it as a combination of a1+b1, a1+b2, a2+b1, a2+b2). Add more atoms and you get even more states, eventually forming continuous bands of energy levels.

It's the same thing, just "smeared out" more. Although in practice they're different fields (solid state physics vs quantum chemistry, typically).

So when the pair jumps from state a1+b2 to a1+b1, the photon that's emitted is different from the one that would be released if the b molecule were alone and went from b2 to b1?

And state a1+b2 doesn't have the same energy as state a2+b1?

Hello? Should I have asked this question in the "Atomic, Solid State, Comp. Physics" section instead?