Rare “Rainbow” Over Idaho

Posted on June 20, 2006  Comments (1)

Rainbow like clouds

Rare “Rainbow” Spotted Over Idaho by Victoria Gilman:

The arc isn’t a rainbow in the traditional sense—it is caused by light passing through wispy, high-altitude cirrus clouds. The sight occurs only when the sun is very high in the sky (more than 58° above the horizon). What’s more, the hexagonal ice crystals that make up cirrus clouds must be shaped like thick plates with their faces parallel to the ground.

When light enters through a vertical side face of such an ice crystal and leaves from the bottom face, it refracts, or bends, in the same way that light passes through a prism. If a cirrus’s crystals are aligned just right, the whole cloud lights up in a spectrum of colors.

One Response to “Rare “Rainbow” Over Idaho”

  1. Circumhorizontal Arcs – Fire Rainbows – Cloud Rainbows » Curious Cat Science and Engineering Blog
    December 20th, 2012 @ 8:52 pm

    [...] form than a rainbow as I learned with a bit of searching online. I added a short post to this blog, about the phenomenon a few years [...]

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