Incredible Fogbows and What Makes Them Happen | Weather
This picture was sent to me from Alan Grime on Mauna Kea and yes that looks like a rainbow, but actually it is not. It is what is known as a Fogbow. What exactly is a fogbow?? I am going to explain to you exactly what one is. Of course if you are a normal reader of the blog you know that I have to explain what causes a rainbow to be able to tell you what exactly a fogbow is and what causes it.
What Causes A Rainbow?
Look at the image below and it will explain to you how the process of how a rainbow forms. Light from the Sun is segmented into many spectrums... The visible spectrum is actually only a very small part of this spectrum. Most of the light coming from the sun we can't even see. Check out the image below to see just how small the visible spectrum is. All of this "visible" light is what we call white light, it is all the colors blended into what we see on a daily basis. When this visible lights hits a raindrop, it reflects off the back of the drop 42 degrees and goes out the front in all the colors. That's right, the white light is bent (refracted for the technical term) and goes back out the front in the most elementary colors. That is how we get ROYGBIV..... red, orange, yellow, green, blue, indigo, violet. This is how you get the huge arc you see in the sky with all the colors of the visible spectrum.
What Causes a Fogbow?
The same thing that happens to a rainbow is exactly what happens with a fogbow, just one MAJOR difference. The determining factor with a fogbow is the fact that water droplets are so small (on the order of 1-100 microns) that the light does not have enough room to scatter into all the visible elements. White light comes in, bounces 42 degrees, then exits the front! You get the arc, just not all the color!
Enjoy the pics!
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