The ray enters somewhere on the drop, which can parameterize by the angle \(\theta\) between the direction of the incoming light and the radius from the center of the drop to the point where the light...The ray enters somewhere on the drop, which can parameterize by the angle \(\theta\) between the direction of the incoming light and the radius from the center of the drop to the point where the light enters. The light that is not concentrated at the minimum value of \(\theta\) is spread inside the first rainbow but outside the second rainbow, thus the region between the two rainbows (or outside the first if the second cannot be seen) is darker.
