Visible light question

Posted by $ AJAshinoff 11 years, 9 months ago to Science
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My understanding of our ability to see things is that objects absorb a wide spectrum of light and only appear to be a specific color because that is the light spectrum it does not absorb. I do understand that the color black absorbs the entire light spectrum to give us the color black.

eg. A fire hydrant is red because red (or a group of spectral colors that comprise red) is the color that the hydrant is not absorbing.

If my understanding is accurate, would an object that absorbs the entire light spectrum (the entire 400 to 700 nanometer range) just appear black or would it appear as a vacant space in its surroundings?
(like a game character that was never colored in or detailed but still moves about the screen)

Any insight that can be given would be most helpful.Thanks in advance.

(yes, this is an element of my new book)
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All Comments

  • Posted by CircuitGuy 11 years, 9 months ago in reply to this comment.
    @LionelHutz My understanding is what you're describing is fluorescence. It's different from reflection, in which certain wavelengths come back unchanged. In fluorescence, you excite it with a short wavelength and the material responds by emitting frequencies consistent with the energy associated with the difference in excited vs non-excited energy levels.
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  • Posted by LionelHutz 11 years, 9 months ago in reply to this comment.
    no problem - but take what I said above with a grain of salt. I don't think it is wrong per-se, but I think it may not be the dominant effect that explains color in typical things. My classes were over 20 years ago and I can't remember context anymore. This might only be the dominant effect in the realm of lasers and such.
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  • Posted by LionelHutz 11 years, 9 months ago
    It's actually not that materials are absorbing all colors but one - it's nearly the reverse of that.
    The way this was explained to me in physics classes is when photons strike materials they add energy to the atoms in the material, causing electrons to jump energy levels. This is a temporary state - the electrons will eventually fall back to their original energy state - causing the emission of photons at precise frequencies which vary depending on the atomic structure of the material in question (basically it depends on how much energy it took to bump an electron up a shell level). "black" really means the object is merely emitting photons in a frequency range that your eye cannot see.
    EDIT: check out web link:
    http://en.wikipedia.org/wiki/Absorption_...)
    Color is apparently a bit messy and has a some of overlapping phenomena in play.
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  • Posted by $ AJAshinoff 11 years, 9 months ago in reply to this comment.
    That what I figured but when you put stuff to paper for public consumption its best to be entirely sure. Thanks.
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  • Posted by khalling 11 years, 9 months ago
    light is either reflected, transmitted or absorbed. There is no way to get perfect absorption, so therefore you'd have some scattered reflection. But if you could get perfect absorption, it would probably look like a black hole in the screen, to use your example (this from db)
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