I was reading Wikipedia article on Rayleigh scattering and came upon this: "...the major constituent of the atmosphere, nitrogen, has a Rayleigh cross section of 5.1×10^(−31) m^2 at a wavelength of 532 nm (green light). This means that at atmospheric pressure, about a fraction 10^(−5) of light will be scattered for every meter of travel." I am embarrassed to say that I am confused how the fraction of scattering per meter has been arrived at, starting from the scattering cross section. I tried the following: dI/ I = -(nitrogen density)*(cross section)*(path length) and you get an exponential decay form but when I calculated the decay constant it was way too small. What am I doing wrong here?