Abstract
I present a model for the computation of the opacity of grains in a protoplanetary atmosphere. The grain size distribution at different levels in the atmosphere is calculated using the microphysics of grain growth via collisions and destruction via vaporization at high temperatures. The Rosseland mean opacity of the resulting distribution can then be computed. The resulting grain opacities are much smaller than those computed assuming a size distribution similar to that of interstellar grains, and is similar to the low opacities used in the models of Hubickyj et al. (2000, 2002).
