Thursday, December 13, 2012

Rainbows

by Vanessa, This post originated at Dear World, ...Sincerely Science.


Everyone is familiar with rainbows, those beautiful arcs in the sky. I feel even more in awe of them after knowing how exactly they are formed.
A rainbow is formed when white light from the sun enters a water droplet. Since the light is entering a new medium the light is refracted, causing the colours that make up white light to break apart and angle away from each other slightly. When the coloured rays hit the other side of the droplet they are reflected. The reflected light then leaves the raindrop, and since it dispersed inside of the droplet it leaves as the colours of the visible light spectrum; red, orange, yellow, green, blue, indigo, and violet. The reason you then see the colours in such a uniformed fashion is because you don’t see all of the escaped colours from each droplet. Say in one droplet the only wave that hits you eye is red, so that is only colour you see. The reason only red travelled to your eye is that it is the only colour that exited at the correct angle to reach your eye.

Here’s where it gets really interesting. Rainbows are actually circles… now let that sink in… okay, carrying on. How can they be circles when you have clearly seen rainbows as arcs in the sky? Here’s the thing, one of the only times you can see a rainbow as a circle is when you’re in a plane, preferably flying it since the pilot gets the best view (also if you are on a very high mountain, but that is even rarer). You know that the light leaves the drop from 41 degrees above normal as well as 41 degrees below the normal (40-42 degrees). Now, say you’re flying a plane, with the sun behind you and a field of raindrops in front of you. You will see the array of colours coming at you from about 41 degrees above you, 41 degrees below you, and 41 degrees from either side. This results in a circular rainbow since the light waves are reaching your eyes from all directions. The reason people on the ground can’t see this is because you can’t see light reflecting out of raindrops from 41 degrees below you, that would mean there would be raindrops reflecting light in the ground… I think that would be a little strange. 
Now, you know the myth that a Leprechaun’s pot of gold is at the end of the rainbow, well with this new found knowledge you know another reason why you could never find the pot of gold at the end of the rainbow. Since rainbows are circular, there is no end. If you somehow could follow a rainbow you would be left traveling in circles for all of eternity, looking for an end that isn’t there. That, in my opinion, is why Leprechauns are so tricky, and why rainbows are so cool!
About this contributor: Vanessa is a high school student with a huge interest in Science, especially Chemistry and Biology. She also enjoys reading, dance, and badminton.

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