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View Diary: Pique the Geek 20110605: Misconceptions about Science (112 comments)

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  •  agreed except (2+ / 0-)
    Recommended by:
    Translator, shantysue

    Water really is blue. Take a look at a light underwater. It looks more bluish than in the air. There's a little tail of the infrared absorption lines that gets up into the red. So it's not at all like the blueishness of the sky, that comes from high-frequency scattering.  I learned this the hard way, after putting an incorrect answer on a public site.

    You might check this description, before the Palinites sack it.

    Michael Weissman UID 197542

    by docmidwest on Sun Jun 05, 2011 at 09:31:11 PM PDT

    [ Parent ]

    •  You used the important term, (1+ / 0-)
      Recommended by:
      shantysue

      scattering.

      Again I say that water is without color.  But it does scatter photons, mostly the high frequency blue ones, and it makes it look blue.

      If you were to irradiate pure water with, say, the sodium D lines, it would be colorless, because that yellow line does not scatter nearly as much at the blue solar ones do.

      I still rest my case.  Water looks blue because of the physics of photon scattering, not because it has a blue chromophore.  May we agree on this?

      Warmest regards,

      Doc

      Fool me once, shame on you. Fool me twice, shame on me. Fool me over and over, then either I really love you blindly or I am a Republican.

      by Translator on Sun Jun 05, 2011 at 09:36:05 PM PDT

      [ Parent ]

      •  absolutely not (2+ / 0-)
        Recommended by:
        Translator, shantysue

        I used to think that and it just isn't true. Water does actually absorb light, not just scatter it. Here's the experiment, easy to do at your neighborhood pool.

        You know that air appears blue because it preferentially scatters blue light. So when you look at a white light (the sun) through air, the light looks reddish, since a lot of the blue has been scattered out.

        Look at a white light under blueish water and it looks blueish. That's because the color comes from absorption of red, not scattering of blue.

        This was gleefully and correctly pointed out to me by a vengeful person whose errors I'd frequently caught, after I'd posted the opposite.

        Michael Weissman UID 197542

        by docmidwest on Sun Jun 05, 2011 at 09:42:48 PM PDT

        [ Parent ]

        •  I just thought about it, and you are right, (0+ / 0-)

          but for a different reason that you might think.

          As I said, water has no UV chromophore, so is is not reactive with visible light.  However, it is infrared active, due the the O-H bonds, and that activity JUST makes it into the visible spectrum, but barely.

          Since to our eyes the lack of red looks green, water does indeed look like a blue green material.  You are correct, and I was wrong.

          Warmest regards,

          Doc

          Fool me once, shame on you. Fool me twice, shame on me. Fool me over and over, then either I really love you blindly or I am a Republican.

          by Translator on Sun Jun 05, 2011 at 09:56:47 PM PDT

          [ Parent ]

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