Optical properties of spherical Mg₂SiO₄ grains as a function of wavelength, calculated for grain radii varying between 0.3–0.7   μm, as well as grains in the small particle limit (a_gr = 0.01   μm, black curves). These properties were calculated from optical data by Jäger et al. (2003), using Mie theory. The shaded area marks the region where most of the stellar flux is emitted. Top panel: the asymmetry factor g_sca. Bottom panel: the absorption and scattering efficiencies, Q_abs and Q_sca, here smoothed to avoid unrealistic resonances inherent to Mie theory.