A Model of Irradiance Distribution for a Directed Point Source in an Infinite Weakly Absorbing Turbid Medium

We propose simple models describing the irradiance distributions for a unidirectional point source in an infinite weakly absorbing turbid medium and also for a narrow light beam obliquely incident on the boundary of a semi-infinite turbid medium. These models involve the same optical parameters of the medium as the formulas of the diffusion approximation of radiation-transport theory. At the same time, the condition of weak anisotropy of the radiation field does not limit the applicability of our models.