The scattering coefficient per particle (\(\frac{\rm{cm}^{2}}{\rm{particle}}\)); \[b_{\rm{scat}}=n\ \sigma _{\rm{scat}}\] where \(n\) is the number concentration of particles (\(\rm{particles cm}^{-3}\)) and \(\sigma _{\rm{scat}}\) is the scattering cross-section. \(b_{\rm{scat}}\), the scattering component of extinction due to gas and particles, is measured in the atmosphere using a nephelometer. For a homogeneous atmosphere it is related in theory to the meteorological range (\(L_{\rm{V}}\)): \(L_{\rm{V}}=\frac{3.9}{b_{\rm{scat}}}\); \(b_{\rm{scat}}\) and \(b_{\rm{abs}}\) represent the scattering and absorption coefficients per unit length for a light beam (of path length \(L\)) which has a spectral radiance (intensity) \(I_{0}\) incident on a sample of air and \(I\) is the transmitted spectral radiance (intensity), \(\ln (\frac{I_{0}}{I}) = L\ (b_{\rm{scat}}+b_{\rm{abs}})\).