If you want an interesting lecture of Snell's law have a look of another MIT lecture
(click here for google video of the lecture) . And you will all understand what's happening to the rainbows... well you first need to know what is Snell's law.
I loved it.
42 degrees is now the angle to remember...
From MIT Physics Lecture: Electricity and Magnetism - 31 - Rainbows
Sorry for the broken links on the google video try this one (Search of MIT lecture)