Summary: reflected by the raindrops under a cloud at an angle of 42 degrees as shown in the picture below The raindrops are not in a vertical plane The rainbow is not as flat as we perceive it The reason why we perceive the rainbow as flat and very far away is that seeing the rainbow is actually a stereoscopic phenomena Your two eyes each see a different rainbow These two
Image Dimensions: 550 x 339
Image originally found here.