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  1. #21
    Photo Engineer's Avatar
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    Well Dan, I'll have to respecfully qubble with your answer. Having seen the spectrophotometric curves of several types of silver, I can say that they vary and none of them absorb between 400 and 700 nm (the human visual range) in a linear fashion, but rather have tilts or humps in their absorption spectra to reflect blue, gree and warm tone images which we have all seen.

    On a single stimulus basis with only one sample in front of us, or under a particular illuminant, a given silver may appear black, but to the discriminating eye or a spectrophotometer it is not.

    PE

  2. #22

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    Quote Originally Posted by dancqu View Post
    A notable example is Global Warming. Carbon
    dioxide is unaffected by incoming wave lengths
    of the spectrum but absorbs out going heat wave
    lengths of the spectrum.
    WHAT?

    Carbon dioxide can absorb IR (heat) radiation coming in as well as going out.

    It absorbs the energy, which causes the CO2 molecule to vibrate at a higher rate that before it aborbed the radiation. It can release the radiation which can then be aborbed by another CO2 molecule, thereby "trapping" the heat. The more CO2, the more heat is retained by the atmosphere.

    But it can do this for radiation that coming from the sun, released by another molecule in the atmosephere, or reflected or released from the surface of the earth.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  3. #23
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    Quote Originally Posted by Kirk Keyes View Post
    But it can do this for radiation that coming from the sun, released by another molecule in the atmosphere, or reflected or released from the surface of the earth.
    I think dancqu meant that the IR heat radiation waves are primarily of "earth" origin, as the earth absorbs the sunlight (full light spectrum) and transmits it partially back into space at longer wavelenghts.
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

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