Glass bead bow

While at work I was on break time I took some blast sand out of the sand blaster and scattered it on the ground and I happened to look down and saw a bright bow around the head of my shadow. The bow is like a rainbow but the higher refractive index of glass made a bow with a radius of 28 degrees rather than 42 for a water drop rainbow. Look for these glass bead bows on reflective signs and freshly painted black top.

Posted by Michael Ellestad


Posted on May 13, 2011, in rainbow and fogbow, theory and tagged , , . Bookmark the permalink. 7 Comments.

  1. Les Cowley said…

    Nice bow Michael. The radius of glass bead bows is about 21 degrees, depending on the type of glass.

  2. Peter-Paul Hattinga Verschure said…

    I sometimes see strongly spectral-colored light patches in sun-lit backgammon-boards which are provided of a special reflection structure. But I never saw a real bow shape, and still certainly not in road surfaces. Although I am a dyed-in-the-wool cyclist. Obviously there always remain chances to see new things!

  3. Marko Riikonen said…

    Michael, your work breaks are very productive. Nice shot.

  4. Michael Ellestad said…

    21 degrees? I always thought it was 28 I need to revise that on my homepage. In some ways Les it reminds me of the road paint bow I got in the smokey MTNS in 2003 when new road edge lines were being painted

  5. Les Cowley said…

    28° – Yes, for some reason that figure is also stuck in my mind. I just happened to be preparing the diagram for Gunther””s seawater bow when I read yours and had to go away and double check!

  6. Les Cowley said…

    Michael – I””ve mailed a little spreadsheet to compute rainbow angles. Glass of n~1.5 will be nearer 22-23 deg.

  7. Michael Ellestad said…

    Yeah I got it but I don””t have MS Spreadsheet I have MS word only

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