Abstract
The optical-NIR opacity law is a key diagnostic of grain growth in protoplanetary disks. We discuss recent determinations of the optical-NIR opacity law from high-resolution images of edge-on disks. Fitting simultaneously for the opacity law and the geometry, and considering an adequately wide range of geometries, yields apparently robust results. In HV Tau C, we find no evidence that the opacity law between 0.8 µ and 2.2 µ differs from that for ISM dust. On the other hand, in HH 30 there is strong evidence that the oapcity law between 0.44 µ and 2.0 µ is much flatter than that for ISM dust, although it is not completely gray. Why the dust in these two objects should be so different is not clear; we discuss our plans to enlarge our sample and investigate if we might be seeing evolution in dust properties between a younger HV Tau C and an older HH 30.
