Absorbed and emitted flux, Q_abs(λ)F_λ and Q_abs(λ)B_λ, for two different grain materials, Mg₂SiO₄ (black) and MgFeSiO₄ (red). The absorbed light is calculated using a geometrically diluted radiation field from a hydrostatic atmosphere (at 2 R_∗ for Mg₂SiO₄ and at 10 R_∗ for MgFeSiO₄) with stellar parameters typical of an M-type AGB star (M = 1 M_⊙, L = 5000 L_⊙ and T_∗ = 2800 K). The emitted light is calculated using a Planckian source function at a grain temperature of T_d = 1000 K. The optical data for Mg₂SiO₄ is from Jäger et al. (2003) and the optical data for MgFeSiO₄ is from Dorschner et al. (1995). We note that the local radiation field in the wind-acceleration zone will be more pronounced in the mid-IR region than what is shown here because of the addition of the emitted light from the dust component.