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Double Rainbow

  1. Oct 18, 2005 #1
    I caught this picture of an unusual double rainbow yesterday after a shower near the zoobie brush shelter here:
  2. jcsd
  3. Oct 18, 2005 #2
    How can you get two rainbows at once?
  4. Oct 18, 2005 #3


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    Staff: Mentor

    Two rainclouds.
  5. Oct 18, 2005 #4


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    Gold Member

    Its called a fogbow, i think (or could be Supernumerary rainbows)


    You can watch the detailed lecture here:

    One sure way to distinguish it is by looking at colour bands themselves. As you can see one has red on outside and one has red on inside, thats why you know its the same rainbow

    Also just by looking at the rainbow you can tell what kind of pollution there is in the area

    Last edited: Oct 18, 2005
  6. Oct 18, 2005 #5


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    Haha no.

    Note the second rainbow is reversed.

    A double rainbow occurs due to a second internal reflection within the raindrops. I good description wouldinlcude a diagram of the refraction properties of the drop of water, but I could not find any online.

    Here is a brief explanation from theweathernetwork.com:

    Double rainbows are not unusual, in fact, they occur with every rainbow. It's just that they are rarely bright enough to be seen.

    When white sunlight enters each raindrop, it bends. The bending breaks light into its rainbow colours. The light then reflects off the back of the raindrop. On leaving the drops the light bends again. [Each raindrop scatters the full spectrum of colours, but you will see only a single colour from each drop]. Sometimes light reflects twice inside the raindrop. This action will form two rainbows: a primary rainbow that is produced by the first reflection of light and a larger secondary bow above the first, produced by the second reflection.

    Colours in the secondary bow are in reverse order to those in the primary rainbow, with red on the inside and violet on the outside. Since only a small number of rays experience this double reflection, the secondary bow is always fainter than the primary.
  7. Oct 18, 2005 #6


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    I stand corrected. :redface: I guess that should be obvious since they are always concentric....
  8. Oct 18, 2005 #7
    i never noticed that they were opposite like that....

    i saw a reall cool one at the mall over the spring. both rainbows were clear from end to end. and the brighter one was absolutely amazing. it looked painted into the sky, mirrored so beautifully by the second one.
  9. Oct 18, 2005 #8
    We caught a rainbow on Sandstone Peak on Sunday. I'd show you the picture but I'd have to upload it. And actually, I can't even find the camera at the moment.

    Your double rainbow is very pretty.
  10. Oct 19, 2005 #9
    wow two pots 'o gold!
  11. Oct 19, 2005 #10
    Hey Zoob,

    Looking over the Conejo and San Fernando valleys, from the highest peak in the Santa Monica range on Sunday:


    The intensity isn't as great as yours. But we enjoyed it!
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