eli5: How exactly does colour absorb light and heat?

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We’re always told that darker stuff absorbs more light and heat and shinny stuff reflect it. How exactly though?

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Yea. How?? Probably has to do with their wavelengths and something something about the materials makeup and colour?

Question is wrong. Color is a manifestation of light, not something that reacts with light.

Each atom has some default energy state.
Light is a source of energy consisting of photons.
When light hits atom, atom can take some amount of energy with specific characteristics from light. If it takes more energy, the weaker light becomes, and when atom cannot take more energy at this given time, you are getting what is left from this light which means some color.
And more energized atom means higher temperature which means more heat streaming from it.

It’s not that the color absorbs the heat, it’s whatever material the object is (or the pigments in the paint) that absorb the heat. Then because of which energies were absorbed all that reflects back is the color we see.

Energy of light is determined by its frequency, E=hf. Frequency of light also determines its color. (Frequency and wavelength are interchangeable, c=fλ)

f=frequency, E=energy, h=Planck’s constant, c=speed of light, λ=wavelength

Every atom has orbitals, the energy states at which the electrons orbit. In order to move an electron from one orbital to another, it needs a very specific amount of energy. If it meets this energy requirement, it will absorb the photon, and reemit any excess energy as a different photon, usually not visible (in the case where it’s visible, we call this fluorescence)

Once you put a bunch of atoms together, the energy levels kind of get blurry, especially with molecules, and you start getting scattering of light, which is why not everything is mirror. The different bonds the atoms make with each other determines which wavelengths of light will bounce off, and which ones will be absorbed or pass straight through.

This is why you can have carbon be black as soot or graphite, or be clear in a diamond.