The blueness of water

[Robert Cohen <Robert.Cohen@PO-BOX.ESU.EDU>]

In the Jan-Feb 2002 issue of American Scientist, there is an article on
Crater Lake.  In the article, it states "The lake's deep-blue color, for
instance, results from the molecular backscatter of downwelling light,
predominantly the short wavelengths in the visible light spectrum."

This raised some questions for me.

1. Is this statement correct?  A recent discussion on this list seemed to
conclude the color of water (and ice) is due to absorption of red, i.e.,
both transmitted and back-scattered light will be blue.

2. In a note by John Denker
<http://mailgate.nau.edu/cgi-bin/wa?A2=ind0105&L=phys-l&P=R8112>, the graph
<http://people.deas.harvard.edu/~jones/es151/pages/gallery/images/water_spec
.html>2> is referenced which does not show any dependence of absorption on
k^n in water.  Is there a k^n-dependence on scattering?

3. Based on past discussions on this list, it seems that the wavelength
dependence of scattering in air can be explained by assuming air molecules
to be small dipoles but density fluctuations in the air are necessary to
explain the k^4 dependence.  Is this correct?

4. My guess is that there would be no density fluctuations in liquid water.
Is this correct?  What about a wavelength-dependence of scattering?
Wouldn't the assumption of small dipoles still be correct?

____________________________________________
Robert Cohen; rcohen@po-box.esu.edu; http://www.esu.edu/~bbq
Physics, East Stroudsburg Univ., E. Stroudsburg, PA 18301