Particle Physics (28 of 41) What is a Photon? 12. Rayleigh Scattering (Why is the Sky Blue?)

In this video I will explain Rayleigh scattering and why is the sky blue?

Next video in the Particle Physics series can be seen at:

[adreanalva]

These are the real heroes. People who make science interesting and easy to understand. Keep doing what you’re doing!

[rainerdbeck]

Just a couple corrections: the fact that Rayleigh scattering is polarized has nothing to do with the shape of the nitrogen and oxygen molecules. Even for spherical molecules and atoms such as methane or argon one observes the same polarization properties of the scattered light which is due to the angular distribution of an electric dipole emitting light and the fact that light is a transverse electromagnetic wave. The electric field of the light shakes the electrons of the molecules which then radiate light with an angular distribution of an electric dipole. Also, the atoms in the molecules don’t vibrate during Rayleigh scattering, it’s just the electrons which are moving in response to the electric field of the light.

[fungkeat]

I am sure you are a polymath, you can teach many topic from totally different industry with huge understand about the course and taught in the way that easily understand by beginner like us and only use a marker pen without any fancy editing, massive respect to you by using a single marker pen and white board to change the world. A massive respect of applied physic student form Malaysia.

[fisterhr]

A great teacher teaching a complex subject in English WITHOUT a thick accent. This is where I would put a lot of value this day in the age of information.

[gravimagswnforce]

Great job in turning complexity into simplicity. It was very insightful. Thank you for sharing the knowledge.

[YouTubist]

Great explanation. I have been wondering how scattering works. Thank you.

[irfanspoetry]

good teaching skills, got understanding easily :)

[bobojr]

Finally I understand why the sky is blue. Love learning this shit. Thank you Michel.

[alphagamma]

Thanks a lot sir. This is one of 5he best video on this topic..

[ellisd]

+Michel van Biezen I get that the purple is 400nm where as red is 700nm lenght. And so blue has longer wave length than purple but less that red. My question is, and what I don't understand for some reason at all, is why doesn't that make the sky purple, since if I understand this correctly, purple should scatter even more than blue?

[josephcoon]

When a molecule vibrates, is not the resultant wave a spherical wave front regardless of the orientation of the molecule?

Oh. I see. The resultant wave front has an amplitude proportional to the angle of incidence.

A resultant wave front is weaker in one orientation versus another. Thanks.

I’ll look around, but I’ve been trying to find an explanation for why reflected light is polarized parallel to the reflective surface while refracted light is polarized perpendicular to the surface.

I am surmising that it has something to do with the freedom of movement for valence electrons as well as the freedom of movement for the nuclei of a crystal’s constituent atoms. Metals having a valence band that is loosely bound to individual atoms creates a kind of sea that has more freedom of movement across the metal’s surface as opposed to perpendicular to it. Whereas a transparent crystal is rigidly locked into its lattice restricting vibrations to along those bonds? Or is the valence band electrons playing more of a role for wave propagation through a crystal more so than the nuclei?

Thanks for your time.

[ИванМорозов-ибя]

thanks for a perfect explanation of this topic
one question left, so in principle, if the molucule just absorbs the photons energy and then emmits it back, the scattering angle is absolute random? or I understand it completely wrong?

[vishnudhakad]

Thank you for awasome lecture
Where to come (derivation) that formula of scattered intercity??

[stellarfirefly]

Why then do we see much more orange/red light during sunrise and sunset time periods? It cannot all be due to the N factor increasing the number of molecules along the light's path, can it? If so, then that would be a very big coincidence that our atmosphere is exactly enough to scatter mostly blue when sunlight shines through it vertically but exactly enough to scatter mostly red when sunlight shines through it largely horizontally.

[adosar]

The wavelengths that are scattered less are absorbed by the molecule ? can we explain rayleigh scattering with quantum mechanics without em waves but photons ?

[chun-weikong]

Dear Biezen, I have a question around 3:17.
Why will the molecules absorb the energy and then re-emit the energy "without loss" ?
The point I couldn't understand is the "without loss" statement.
May you please explain about it?
Thank you very much!

[pfc-]

Beautiful presentation, thank you so much!

[SogMosee]

So does a single ray of light get split into multiple rays of light after it is absorbed and re-released from the electron? If so, does that mean subsequent ray of light is weaker or less energetic than the parent ray of light? Your illustration seems to imply this.

[jakubkusmierczak]

But scattering means changes in frequency lenght or amplitude of the wave or it has something to do with photon particle i. e. it is phisical collision? Best greatings and thank You.

[redzuantahar]

Hello. You mentioned Nitrogen & Oxygen molecules. Can you help elaborate about interactions with aerosols? And how that would be different or similar?