why sky is blue?

**kambez** · Nov12-09, 11:20 PM

Hello everyone!

Can anyone explain why sky is blue?

Thanks.

**chroot** · Nov12-09, 11:22 PM

Because the atmosphere is better at scattering blue light than light of other colors.

- Warren

**Bob S** · Nov13-09, 02:31 PM

See Rayleigh scattering in our atmosphere:
http://hyperphysics.phy-astr.gsu.edu...os/blusky.html
The scattered blue light is polarized because of this.
Bob S

**tiny-tim** · Nov13-09, 02:43 PM

Hello kambez! Welcome to PF!

It's because scattering is inversely prooprotional to the fourth power of wavelength … see http://en.wikipedia.org/wiki/Rayleig...from_molecules …

The strong wavelength dependence of the scattering (~λ−4) means that blue light is scattered much more readily than red light. In the atmosphere, this results in blue wavelengths being scattered to a greater extent than longer (red) wavelengths, and so one sees blue light coming from all regions of the sky. Direct radiation (by definition) is coming directly from the Sun. Rayleigh scattering is a good approximation to the manner in which light scattering occurs within various media for which scattering particles have a small size parameter.