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Amazing rainbow!

  1. Jun 1, 2005 #1

    Chi Meson

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    Last evening there was the perfect rainbow condition: A bright evening sun shining into a rainstorm just overhead. I went outside to see both complete arcs from horizon to horizon . THen...

    the inner rainbow (the most commonly seen rainbow, with red on the outside of the bow) looked odd: instead of blue on the inside, it was definately magenta. Then I noticed that the entire cycle of colors repeated a total of four times. Each cycle overlapped the red on top of the previous blue (hence the magenta). Each cycle got fainter and tighter together so that I assumed that it continued ad infinitum but was too faint to be seen after the fourth order. I have never seen nor heard of this rainbow phenomena before. My only guess is that this is due to sunlight internally reflecting inside the raindrop for one, two, or three laps inside the drop before refracting out.

    Has anyone heard of, or seen, or have an explanation of this?
  2. jcsd
  3. Jun 1, 2005 #2
    the rain bow originates from a process called chromatic dispersion, ie the different frequencies that make up the incident sun light (EM-wave) each are reflected under a different angle. The fact that such patterns repeat themselves is due to the interference of the reflected waves. This is just like the thin film interference on an oil-spot on the ground. Some times there will be reagons where it is dark. Light is reflected but there is destructive interference of the eflected waves. This is dependent of several facteros, the thickness of the oil-film being one of them


    go check out hyperphysics http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

    chose light and vision and then atmosferic phenomena
    Last edited: Jun 1, 2005
  4. Jun 1, 2005 #3


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    Hey, we got that here, too - Sunday night. I'll post my pics later...
  5. Jun 1, 2005 #4

    Chi Meson

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    Great site, thanks. So, the name of these things are "supernumerary arcs." After a google search I found this explanation
    http://www.sundog.clara.co.uk/rainbows/supform.htm [Broken]
    which is, like Marlon said, more similar to thin film interference. All sites I looked at said simple geometric/refraction explanations fail.
    Last edited by a moderator: May 2, 2017
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