Re: feather color

[John Denker <jsd@MONMOUTH.COM>]

At 10:11 PM 1/9/01 -0600, cliff parker wrote:

> interference such as that observed in thin films such as
> soap bubbles?

Yes.  Interference effects are responsible for the colors of
 -- feathers (mallard, hummingbird, peacock)
 -- Morpho butterfly wings
 -- mother of pearl (abalone, oyster)
 -- those funny anti-counterfeiting features on money and product labels
 -- etc.

> If so then there must be some transparent material
> covering the wings.  Is this the case?

Yes.

> What do you mean by nearly spectral?

Spectral refers to the pure colors of the spectrum.  Monochromatic would be
a more technical term.

Most students have little familiarity with really pure colors.  Even the
colors of the rainbow are not particularly pure, as you can see from the
curves in _The Feynman Lectures on Physics_ or from the nifty applet at
  http://www.phy.ntnu.edu.tw/java/Rainbow/rainbow.html

The interference colors of a _single_ layer are not particularly pure,
either.  However, by using multiple layers, you can make a very very sharp
filter.  These colors are much more pure than any dye or pigment.

> Nice try, but it is too late for me to be looking up such things.
> However if you are inclined to make things easy on me I would be
> interested to hear more about these interesting etymologies.

Hmmm.  If it's too late to open a dictionary, perhaps it is too late to
send email to 600+ busy people.
  http://machaut.uchicago.edu/cgi-bin/WEBSTER.sh?WORD=Iridescent