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Why is the sky blue?

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Re: Why is the sky blue?

#2

Post by ranger_danger »

Here is a wonderful lecture with real-world demonstrations of the effect:

https://www.youtube.com/watch?v=4a0FbQdH3dY

https://en.wikipedia.org/wiki/Rayleigh_scattering

I do have a question though.

The article says:

> blue and violet have the closest frequencies to a “resonant frequency” of nitrogen and oxygen molecules’s electron clouds

I thought it was more to do with the photon frequency matching the physical size of the air molecules? Or is that the same as its resonant frequency?

Re: Why is the sky blue?

#4

Post by AndrewKemendo »

ranger_danger wrote: post #2

Here is a wonderful lecture with real-world demonstrations of the effect: https://www.youtube.com/watch?v=4a0FbQdH3dY https://en.wikipedia.org/wiki/Rayleigh_scattering I do have a question though. The article says: > blue and violet have the closest frequencies to a “resonant frequency” of nitrogen and oxygen molecules’s electron clouds I thought it was more to do with the photon frequency matching the physical size…

Fs is the frequency at which whatever your measuring is most efficient at vibrating

So it’s a combination of the composition of the thing and the environmental coupling with other vibrating things

Size and material composition are the primary factors

So for this case, the photon spectrum interact with nitrogen-oxygen mixture most efficiently at the frequency that reflects blue

I mostly studied sound frequency mixing with static objects (matching or cancelling the fs of room/space with the fs of a driver) but the principles of resonance hold across media

Re: Why is the sky blue?

#5

Post by KellyCriterion »

Interesting here is: Actually, for most blue butterflies, it’s not even a pigment-it’s just a trick of the light. Since blue is so rare in the biological world (hardly any plants or animals can produce real blue chemicals), they evolved structural colors. Their wings have these microscopic ridges that reflect blue light while canceling out other colors.

It’s basically the same reason the sky looks blue, just built into a wing. If you were to look at the wings from a different angle or get them wet, the blue often disappears because you're messing with that physical structure

Re: Why is the sky blue?

#7

Post by pfdietz »

ranger_danger wrote: post #2

Here is a wonderful lecture with real-world demonstrations of the effect: https://www.youtube.com/watch?v=4a0FbQdH3dY https://en.wikipedia.org/wiki/Rayleigh_scattering I do have a question though. The article says: > blue and violet have the closest frequencies to a “resonant frequency” of nitrogen and oxygen molecules’s electron clouds I thought it was more to do with the photon frequency matching the physical size…

Air molecules are much smaller than the wavelength of visible light, by several orders of magnitude. This is why you can't resolve individual molecules in an optical microscope, and why photolithography with visible light doesn't go down to molecular feature sizes.

Re: Why is the sky blue?

#10

Post by renewiltord »

ranger_danger wrote: post #2

Here is a wonderful lecture with real-world demonstrations of the effect: https://www.youtube.com/watch?v=4a0FbQdH3dY https://en.wikipedia.org/wiki/Rayleigh_scattering I do have a question though. The article says: > blue and violet have the closest frequencies to a “resonant frequency” of nitrogen and oxygen molecules’s electron clouds I thought it was more to do with the photon frequency matching the physical size…

https://www.youtube.com/watch?v=4a0FbQdH3dY&t=2038

Direct link to timestamp 33:56

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