The Barri washhouse and interference phenomena

The Barri public washhouse is located in the middle of the village of Saint-Michel l'Observatoire, in Haute Provence (France).
At the beginning of the last century, the washerwomen came to wash their clothes at the Barri washhouse. It is made up of several pools.
A close-up on the first pool reveals complex wave interference phenomena produced by turbulent water movements. The water then falls drop by drop into the second pool, producing beautiful circular waves that propagate very peacefully. In the third pool, several waves produced in different places sometimes lead to beautiful interference phenomena. These phenomena are made magically observable on the back wall of the washhouse, after reflection of the Sun's rays on the water surface. They are only visible at certain times of the day and year (cf. end of August around 10 a.m.).