Tuesday, June 10, 2008

Why sun rays appear yellow

Today I've made a great discovery! Great in my context but of course infinitely small in your context, I think I know why sunlight appears to be yellow, or sun rays appear to be yellow especially when there are no clouds and the sky is perfectly blue!

I was giving tuition and while my student was doing the questions, I came across the color triangle, and I happened to see that yellow is just a combination of red and green with absolutely, I repeat, absolutely no blue inside! And light dawned on me, yes, pure white light dawned on me! The mystery of the apparent yellow we see I think is because white light, on its way from the sun to the earth, would hit the dust particles in our atmosphere and thus caused most of the blue light to scatter. As for Reyliaugh's formula, I have no idea how he derived it and why is that a larger wavelength would have a much larger probability of being scattered. And since most of the blue light is scattered, what is left behind would be green and red and therefore, the sun rays appear yellow!

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