# What's the relationship between an object's color and it's energy?

All else held equal, which has more energy: a violet-painted teacup or a red-painted teacup?

I know that violet light has more energy than red light, but does this mean that the inverse holds true for painted things? Does red paint necessarily hold more energy than violet paint? Or is the reflective property not related to energy in any way?

I understand that electron energy levels have to do with the color of light emitted, but is there a correlation between the total energy in the material and the color that it reflects?

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Good question. IMO that depends on which is the fate of the rest part of spectrum (whether the other frequencies are absorbed in or transmitted through the teacup). – Leos Ondra May 16 '12 at 18:49
Assume opaque teacups. The question becomes trivial if one absorbs high-energy light and the other reflects it: a better phrasing might be "Assume you have two otherwise-identical materials. One reflects only red light, the other only violet. In darkness, with no light shining on them, can we say definitively that one has more energy than the other?" (Also, if so, what form does this energy take? Potential energy of the electrons orbiting the atoms?) – So8res May 16 '12 at 20:03

Or is the reflective property not related to energy in any way?

Correct.

If you were talking about the color of light emitted by the teacups (because they were heated in a furnace until they glowed) then there would be a relationship between color and temperature, but the color of light emitted would depend more on temperature than paint.

If you put them outside in the sun, they'd absorb the sun's light differently, and change in temperature differently, but if you're just talking about two otherwise identical teacups in a dark box not interacting with the outside world, they would have the same energy no matter what color they were painted.

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Interesting. So what is it, then, that differentiates two teacups in a dark box not interacting with the outside world but wich would reflect different colors? Does it have to do with the configuration of the surface? – So8res May 16 '12 at 21:16
@So8res: Not sure what you mean, but in order for them to reflect differently in the presence of light, they'd need surfaces painted with different chemicals. – endolith May 16 '12 at 21:19
Correct. I'm wondering if you can glean anything about the chemical by knowing only what color it reflects. In other words, what is the minimum difference between chemicals to cause the reflection of different colors; and what does that difference entail. – So8res May 16 '12 at 21:35
@So8res: Well, you can use spectral analysis to identify chemicals, yes, but I doubt it's a simple relationship. For anything other than hydrogen, the spectrum is very complex, and spans a much wider range than human vision. The parts that happen to fall within our visual range and affect our color perception would be pretty random/chaotic, I think. – endolith May 16 '12 at 23:12

I think you are confusing a couple of things here.

There is a relationship between an objects color and it's temperature (at least for black objects) and there is a relationship between the wavelength (color) of a photon and it's energy

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I understand that -- but is there also any relationship (albeit indirect) between the percieved color (reflected light) and the energy (likely w.r.t. electron energy levels in the object)? – So8res May 16 '12 at 19:32
There's a relation ship between the reflected color and the available electron levels - from the wavelengths absorbed – Martin Beckett May 16 '12 at 19:53
Yes, I know. But what is the relationship? Can we say that, all else held equal, the red teapot has "more energy" than the blue? If you have otherwise identical materials, but one is reflecting blue light and the other red, which is more energetic? – So8res May 16 '12 at 19:57