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



By coincidence I have only recently made a classroom poster about this
phenomenon (part of a series I'm putting together) and I was wondering
just the same thing! As you can see, I couldn't find the right word
either:

https://physicsfootnotes.com/wp-content/uploads/2017/05/Caustics.pdf

(Feel free to use it if you like it btw)

Words like 'web', 'mesh', and 'network' come to mind, but none work
well.

So I second JD's question!

Derek McKenzie
PhysicsFootnotes.com



-------- Original Message --------
Subject: [Phys-L] swimming-pool caustics and spangles ????
From: John Denker via Phys-l <phys-l@mail.phys-l.org>
Date: Sat, June 03, 2017 3:33 am
To: Forum for Physics Educators <Phys-L@Phys-L.org>
Cc: 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?
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