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Main Question or Discussion Point
We see an object coloured because of the component of light reflected by it. But what is in the object that makes other wavelengths absorbed by it and one to reflect.
The atomic composition. Gold, for example, is all one kind of atom and so has a single characteristic wavelength that is emitted by the excitation caused by impinging photons. The impinging photons have various levels of energy and when they are strong enough, they cause the electrons in the gold atoms to jump up one energy state and when they drop back they produce one "gold" photon that then impinges on our inner eyes and our brain interprets it as what we call "gold". The energy not so used by the photons hitting the gold goes into making the bar of gold slightly hotter.We see an object coloured because of the component of light reflected by it. But what is in the object that makes other wavelengths absorbed by it and one to reflect.
In a dense medium like a metal, the electrons do not "jump up an energy state". There is a continuum of energy levels (an energy band) and transitions of all values between limits can have any value. It is important to recognise that the H Atom model is not enough to deal with solid state situations. The reflection will be coloured slightly because of the details of the metal structure where certain frequencies may lose a different amount of energy in the reflection process.The atomic composition. Gold, for example, is all one kind of atom and so has a single characteristic wavelength that is emitted by the excitation caused by impinging photons. The impinging photons have various levels of energy and when they are strong enough, they cause the electrons in the gold atoms to jump up one energy state and when they drop back they produce one "gold" photon that then impinges on our inner eyes and our brain interprets it as what we call "gold". The energy not so used by the photons hitting the gold goes into making the bar of gold slightly hotter.
Interesting. Thanks for that correction.In a dense medium like a metal, the electrons do not "jump up an energy state". There is a continuum of energy levels (an energy band) and transitions of all values between limits can have any value. It is important to recognise that the H Atom model is not enough to deal with solid state situations. The reflection will be coloured slightly because of the details of the metal structure where certain frequencies may lose a different amount of energy in the reflection process.
This only applies in the case of gases. In dense media, there is a continuum of energy states within 'bands', rather than isolated levels. Often, within a wide band of energies, the light (other EM wavelengths also ) can be absorbed and give the surface 'colour'. You never get monochromatic light with pigments and dyes.A basic example is green plants, the chlorophyll in the leaves absorbs the red and blue for energy and the green is reflected.
I googled and found this: https://www.itp.uni-hannover.de/~zawischa/ITP/origins.html
Haven't gone though that page yet, but I'm pretty sure it has to do with the surface texture for the simple case of reflection, various atoms also absorb distinct narrow bands as the energy per photon has to be exactly right to bump an electron n shells further from the nucleus (like phinds said), and just the first few seconds of scanning that webpage shows it can get a lot more complicated than just simple "this makes it red, this makes it green, this makes it blue"
Thank you. You have given a very good and logical explanation. Thanks again for the answer.In a dense medium like a metal, the electrons do not "jump up an energy state". There is a continuum of energy levels (an energy band) and transitions of all values between limits can have any value. It is important to recognise that the H Atom model is not enough to deal with solid state situations. The reflection will be coloured slightly because of the details of the metal structure where certain frequencies may lose a different amount of energy in the reflection process.
I was debating on the gas chromatograph approach with colored flames, etc. or the organochemical basis which really seems simple from what I'm reading... I'm into the energy diffusion widening the spectral bands (like you were heading it seems) related to the freedom of electrons transiting the double bonds in molecules.This only applies in the case of gases
It means that it depends on the type of atoms but what about that lizard which changes its colour.In a dense medium like a metal, the electrons do not "jump up an energy state". There is a continuum of energy levels (an energy band) and transitions of all values between limits can have any value. It is important to recognise that the H Atom model is not enough to deal with solid state situations. The reflection will be coloured slightly because of the details of the metal structure where certain frequencies may lose a different amount of energy in the reflection process.
I put it down to the Paui Exclusion Principle, basically. Nearby atoms cannot have the same states so they mutually widen the lines into bands.I was debating on the gas chromatograph approach with colored flames, etc. or the organochemical basis which really seems simple from what I'm reading... I'm into the energy diffusion widening the spectral bands (like you were heading it seems) related to the freedom of electrons transiting the double bonds in molecules.
Lizards (chamaeleons?) and several fish / octopi, have tiny sacs of different pigment that they can squeeze and control which pigment is closest to the surface. It works like Pointilistic Painting and an inkjet printer. No actual 'chemistry' involved to vary the colour.It means that it depends on the type of atoms but what about that lizard which changes its colour.