Caustic Observations

Yuba River with Caustics, September 2011

As often happens, I find something on the internet that reminds me of something else. It sends me on a journey, and I learn something new in the process. I absolutely love when that happens. And, it makes me want to share it with you.

One of my favorite websites Atmospheric Optics has been on vacation. I still check in every now and then just to see which photos from their archives is up on the front page. I also often use the search option to research some optic phenomenon. I checked in on Monday and found this photo posted there. It's an optic called a Skypool, a phenomenon of the shape of water surface and color. It reminded me of something I had shot a few years ago at the Yuba River. I did a post on it back then. Here's a link to that old post.

Closeup of Caustics

I wrote Les Cowley at Atmospheric Optics and sent him the above photo. I asked if these rainbow ripples on the Yuba were skypools. I heard back from him, and he delightfully informed me that they were not skypools, but rather caustic optics. CAUSTICS? I had never heard of such a thing, and yet there I had been photographing it two years ago! Les wrote:

Your shifting spectral colours and bright patterns are something else – ‘caustics’ on the river bed.     The name caustics is said to come from their appearance of being sharply focused sunlight that would scorch like a burning glass.  The lines on the sea or river bed are mostly unsplit into colours – or at least not significantly.    The flashes of colour happen when a sharply tilted wave acts like a prism to split the image of the white line into a spectrum.    

Caustics on the Yuba River

I was surprised to see that even Wikipedia has a page devoted to the phenomenon. Who knew? Certainly not me. And now you know! The planet is full of such beautiful phenomenon. I would like to learn something new everyday. How's that for a dream of growing old!