What is the intensity of sunlight required to form a rainbow. I read in the love of physics by Walter Lewin than
"“For you to see a rainbow, three conditions need to be met. First, the Sun needs to be behind you. Second, there must be raindrops in the sky in front of you—this could be miles or just a few hundred yards away. Third, the sunlight must be able to reach the raindrops without any obstruction, such as clouds.”
I did not understand the third point.