Double Rainbow

Dear Friends
last Friday me and our Etienne, we embarked in a long journey of about 12 hours of car from Munich to Vaas (Sarthe - FR): http://fr.wikipedia.org/wiki/Vaas
for visiting some sites hosting military structures of the WWII. The journey has been anything but comfortable due to at least ten thunderstorms we met crossing France. However, our endurance has been rewarded by a superb double rainbow after one of them. The images present you the double rainbow. Why the internal rainbow has a composite structure and why the area between the internal rainbow and the external rainbow is darker than the areas outside said rainbows are questions that have not yet found a scientific explanation alo by involving the Quantum Mechanics. In case of interest please let me have your feedback.
Salutations
Giancarlo