

It’s related to the number of total internal reflections inside a raindrop. The 2nd rainbow is actually inverted, colour wise. The 3rd inverts again, and so is normal. Each reflection loses more light however, so it gets dimmer. 3 is the practical limit in the sky, with our eyes. In the lab version, at least 18 rainbows can be detected, even by undergraduate level students!








Not infinite. Eventually they begin to overlap and are no longer distinct rainbows.