What causes the shadow below a whirlpool in a pool?

[Big_E_Pat]

Hi there,

I have noticed that when the wadding pool I work at is draining, a small whirlpool appears over the drain in the center of the pool. When the sun is shining a shadow appears at the bottom of the pool(2.5-3 feet deep) below the whirlpool. The shadow is larger than the whirlpool itself, or at least larger than the amount of water that is noticeably moving.

Using my knowledge of physics, I hypothesized the moving water perhaps diffracts the incoming photons so that a minimal amount pass through, therefore causing the shadow at the base of the pool? Any help would be greatly appreciated, this has been really bugging me.

Please excuse my grade 12 knowledge of physics.

P.S. I took a picture, but cannot upload it due to iphoto "unexpectedly quitting" on me whenever i try to open it, i hope i have been descriptive enough.

Thanks,

Eric

 

[chrisbaird]

The clear water "refracts" the light, not "diffracts". The curved tops of the ripples act like lenses and bends the light. The spots where the light is bent away from look darker, but there should also be lighter spots on the bottom of the pool where the light has been bent towards. You can play around with this effect using eyeglasses.