I'm trying to understand, in terms of cross sections, why is the sky blue? Intuitively, blue has a smaller wavelength than the rest of the colors so it can "see" the internal structure of atoms and get scattered.
However, how do we quantify that using cross sections? I read in a book that for resonance, the cross section behaves like ε/ΔΕ where ε is the photon's energy and ΔΕ the state's energy uncertainty. It seems that the larger the energy, the higher the cross section, so the higher the probability that the blue light causes an electron to jump to a higher state - and then, because of the symmetry of the process, the higher the probability of the spontaneous emission to emit blue photons. Is this correct?
I looked at other posts but couldn't find an answer with cross sections.
