The scattering coefficient per particle (cm2/particle); \[b_{\text{scat}}=n\ \sigma _{\text{scat}}\] where n is the number concentration of particles (particles cm-3) and σ scat is the scattering cross-section. bscat, 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 (LV): LV = 3.9/bscat; bscat and babs represent the scattering and absorption coefficients per unit length for a light beam (of path length L) which has a spectral radiance (intensity) i0 incident on a sample of air and I is the transmitted spectral radiance (intensity), ln ( I 0 I ) = L ( b scat + b ab.