[Phys-L] swimming-pool caustics and spangles ????

[John Denker <jsd@av8n.com>]

Hi Folks --

Here's a seasonal bit of physics:

Oftentimes on a sunny day, ripples on the surface of a
swimming pool make beautiful, complicated patterns of
light on the bottom.

A big part of the story has to do with /caustics/.  That's
according to people who have thought about it more than I
have.  See e.g. figure 1 here:
  http://wwwmpa.mpa-garching.mpg.de/mpa/research/current_research/hl2011-7/hl2011-7-en.html
also
  https://en.wikipedia.org/wiki/Caustic_(optics)

People in the swimming pool industry call the patterns simply
"ripples" but IMHO that's a misnomer.  I say ripples on the
top of the water explain the caustics on the bottom.

In any case, there's more to the story.  The /brightest/ parts
of the pattern are presumably caustics, in the strictest sense
... but is there perhaps a nice name for the pattern as a whole?
Sparkles?  Spangles? ?????????

Any suggestions?