Application of the method of the separation of fluxes to the reflection of light: Calculation of the partial reflection function for a linear scattering phase function

In this paper, we continue the investigation of the reflection of light from a semi-infinite medium. For a medium with a Linear scattering phase function, we use the method of separation of fluxes to calculate analytically the first partial reflection function (FPRF) S-(1) in the case of the normal incidence of radiation upon a surface of a medium. The FPRF is compared with the exact reflection function (RF) calculated using the Ambartsumyan formulas. In the case of the oblique incidence of radiation upon a surface of a medium, we also calculate the FPRF integrated over the azimuth and compare the obtained results with the predictions of the Ambartsumyan theory. We analyze the influence of the single-scattering anisotropy on the accuracy of the S-(1)-approximation. It is demonstrated that the FPRF describes the main features of the spectrum of reflected radiation, and the remaining reflected radiation, formed by photons that change the sign of their velocity projection c(z) on the z-axis three and more times, is described by a dependence close to a cosine function.