Look, There's Another One!

What Makes a Double Bow?

Some days when there is rain and shine together, a rainbow can be seen. This is an awesome enough occurrence in itself, but there is something even greater that can occur on the days that it both rains and shines; a double rainbow! They are rare, so what makes this rare wonder seen.

  • A double rainbow consists of a primary bow and a secondary bow.
  • Raindrops that cause a primary bow are much lower in the sky than those that cause the secondary bow, and they only refract and disperse the incoming light once.
  • The secondary bow, on the other hand, is produced from raindrops that are higher in the sky, and refract and disperse light twice. Below is a diagram that show this process.


The most interesting part of a secondary bow is that the colors are switched. Light is refracted and dispersed twice in the drops that produce a secondary bow. This causes the colors to come out in the opposite order of the primary bow.


Below is a photo of a double rainbow. On the left is the secondary bow and on the right is the primary bow. Althought the secondary bow is faint, it can be seen that the colors are switched.