Wavelength dependency of wave-object-interactions. What a title! :-) But that is exactly what I observed over the enormous timespan of three full minutes (as shown by the time stamps of my camera) when I went strolling along Kiel Fjord one Saturday morning.

First, I saw this old, overgrown tyre in a wave field that was dominated by small wind waves. We clearly see how they are diffracted around the tyre and how there is a nice interference pattern downwind of the tyre (to the left in the picture below).

Tyre in the Kiel Fjord and diffraction of small wind waves around it, leading to a beautiful interference pattern to the left of the tyre

Also I quite like how there are absolutely no waves inside the tire, where the wind is shaded off by the tyre and the stuff growing on it.

Then, a really short while later, the wave field was dominated by longer waves running in from the distance. Below, we still see remnants of the old interference pattern to the left of the tyre, but also how the longer waves run around it. In the picture below, the wave crest that was broken up by the tyre is about to rejoin.

And then, only an instant later, this is what the wave field looked like. Hardly and ripples caused by local wind, but many short waves. No real interaction between tyre and waves visible any more.

Isn’t that fascinating? And it all happened within three minutes! :-)

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