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?