Quesitons about scattering of light

Jun 2014
67
0
I have several questions about the scattering of light.

Air molecules scatter sunlight and makes the sky blue, many books say that the air molecules are oscillated by E field and so they becomes sources of EM wave. Is it because the air molecules have charges? I wonder if air molecules or molecules of other medium (e.g. water) are completely neutral (i.e. no excess charges at all), will they still be oscillated by the E field and scatter light?

Air molecules can be oscillated by E field and re-radiate EM waves in different directions. However, if light is shined to a conductor the E field oscillate the free charges but the effect is to reflect the light or dissipated the energy by electrical resistance. Why there is such a difference?
 

ChipB

PHF Helper
Jun 2010
2,361
289
Morristown, NJ USA
many books say that the air molecules are oscillated by E field and so they becomes sources of EM wave. Is it because the air molecules have charges?
No - air molecules (primarily N2 and O2) are neutral in charge. The EM field sets up a dipole charge displacement in the molecule, and the oscillation of the dipole results in emission of light from the molecule.

I wonder if air molecules or molecules of other medium (e.g. water) are completely neutral (i.e. no excess charges at all), will they still be oscillated by the E field and scatter light?
Again, the molecules are electrically neutral. And yes - water can scatter light, but gasses are more efficient at it than liquids.