Effects of dust on the formation of lines in an expanding spherical medium

We have computed a series of line profiles formed in a spherically symmetric and radially expanding atmosphere in which dust is presented. We assumed that the dust scatters radiation isotropically. Two cases of dust distribution are employed: (1) uniform distribution of dust through out the medium and (2) density increasing with radius. The density and the velocity of expansion of the gaseous component are assumed to satisfy the equation of continuity. We assumed a model of two-level atom in non-LTE approximation with complete redistribution. The calculations are done in the comoving frame of the fluid and later transformed to a point a infinity