Why are rainbows shaped like an arch?
Imagine looking at a rainbow off to the east. The sun is setting behind you in the west. White sunlight (a combination of all the colors in the rainbow) travels through the atmosphere, flies eastward past your head, and hits the water droplets as they fall from a passing storm. When a beam of light hits one of these droplets, one of two things can happen: The light could simply pass through, or, more interestingly, it could hit the front of the droplet, bend as it enters, then reflect off the back of the droplet and leave through the front, back toward us. This is the light that forms rainbows.
The amount light bends as it passes through the droplet depends on the light's wavelength, or color -- red light bends the most, orange and yellow slightly less, and so on, down to violet, which bends the least.
Since each color is bent through a specific angle -- red light comes from the sun and is reflected back at an angle 42 degrees away from its original direction, while blue light bends only 40 degrees -- each color appears at a different place in the sky. Red, say,
denotes all those locations in the sky 42 degrees away from an imaginary line connecting the sun to the back
of your head. Together, these places trace out an arch. Since blue appears only 40 degrees from this imaginary line (which also connects your head to its shadow), the blue arch of a rainbow
is always below the red.
I am confused, because when I look at different sources they seem to disagree about whether light with shorter or longer wavelengths pass through prisms or raindrops faster. Physicsclassroom.com says that RED light passes through faster, meaning it refracts (or bends) less than violet light (which has the shorter wavelength). http://www.physicsclassroom.com/class/refrn/u14l4a.cfm
Wikipedia also suggests that red light, with longer waves, actually bends less than violet light.
I'm not a physicist, but I believe that you may be incorrect in this article. From the other sources I've read it seems to me that violet light is slowed down more when it enters a different medium, and so bends more. Perhaps there's a difference between the affect of water on light as compared to that of glass, or a prism on light? Can you "shed some light" on your sources regarding your statement that "red light bends the most, orange and yellow slightly less, and so on, down to violet, which bends the least."
I just want to make sure I'm teaching the correct science to my students! Thank you!
Here's another site which states the opposite of your claim about which color light bends more:
I havent got the actual answer which i was expecting,but somehow i got the good results..after total internal reflection and refraction..there is one more important event that occurs which only decides the arch shape of the rainbow ie interference of the light waves. When these light waves which comes out after refraction..from different drops...interfere to form arch.i know that u are going to pull my ears because i havent elucidated it well. But thats a homework for u..