Pretty (and Mysterious?) Water “Shadows”
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Freaky Water “Shadows” -- Rootstown, Ohio, USA -- Copyright 2009 Jeffrey Friedl,
Nikon D700 + Nikkor 70-200mm f/2.8 @ 135 mm — 1/400 sec, f/9, ISO 220 — map & image datanearby photos
Freaky Water “Shadows”

While filling the kiddy pool mentioned in the previous post, two blades of grass got into the water and made interesting “shadows” on the floor of the pool a foot below.

Here are some close-ups...

Sometimes you see these in larger pools or fountains created by invisible eddies on the surface. They're always pretty and somewhat mysterious because they seem to be shadows of nothing, or at least much larger than the thing that seems to be creating them.

Of course, they aren't shadows at all. I'm sure someone's done all kind of research about them (and I'm sure the phenomenon must have a name), but just putting a bit of thought into it makes you realize that the very slight indentation in the surface of the water due to the weight of the blade of grass acts like a lens, refracting the light off to one side or other. The dark “shadows” have bright edges, because that's where the bulk of the refacted light has been diverted.

I wonder whether Richard Feynman ever contemplated them. He could probably do the math in his head. Just thinking about someone thinking about the math makes my brain melt. I'll stick with “hey, look, pretty!”

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