Will neutral particles be affected by EM waves? Air molecules scatter sunlight and makes the sky blue. Many books say that the air molecules are oscillated by E field and so they become sources of EM waves. 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?
 A: A model for the interaction of light with atoms and molecules treats the charge distribution as an electric dipole, because the particles consist af separate positively and negatively charged particles that can be polarised to have a non-zero electric dipole moment. Neutral particles where no (internal) charge separation is possible should not be affected by EM waves.
This electric dipole oscillates in response to the applied oscillatory electric field from an electromagnetic wave and can be thought of as a damped, driven harmonic oscillator.
The oscillating dipole in turn generates electromagnetic waves, but these waves are not just emitted in the same direction as the incoming radiation. In other words, the power of the incoming radiation is scattered.
This simple, classical analogy is able to explain the phenomenon and wavelength-dependence of Rayleigh scattering (which is why the sky is blue) and also offers a simple description of why atoms/molecules absorb and scatter light particularly well at resonant frequencies associated with the difference in energy between quantum states. However, the classical analogy fails when trying to describe spontaneous and stimulated emission.
A: Electromagnetic waves are produced whenever charged particles are accelerated, and these waves can subsequently interact with any charged particles, they dont interact with neutral particles.Though I do remember reading somewhere that neutral particles can lead to acoustic waves but I dont remember the concept or conditions involved or the equations.
