I must confess I had to head to Wikipedia for that one
But basically in some cases you get a reflection inside the water droplet, so whilst most of the light is refracted through to form the first rainbow, a small amount of it is reflected back in a different direction. Obviously, in order to leave the raindrop, it must go through the same refractive process, and so you see a feinter secondary rainbow.

As for the end of the rainbow, this picture might partly answer your question.
(LongJohnBaldry, Thu 25 Mar 2010, 12:23, 1 reply, 16 years ago)

oooh wow
I was hoping that would be the answer, now I can pursue my official career as a rainbow hunter!!

Thanks for that, I feel enlightened.
( Kitty v1.0 desperately naive, Thu 25 Mar 2010, 12:33, Reply)

You're very welcome
There's something very satisfying about imparting knowledge to someone else. Especially if they understand whatever I'm blithering about.
*is satisfied*
(LongJohnBaldry, Thu 25 Mar 2010, 12:36, Reply)