The near/mid-IR extinction for spherical grains. The curves show the opacities corresponding to 0.1 μm spheres of silicate (light gray) and graphite (black). Dark gray curves correspond to a 1:2 mix of graphite to silicates of 0.1 μm grains (solid gray curve) and for the MRN distribution (dashed curve). The dotted curve shows the adopted continuum for calculating κ_sil, the amount of extinction in the 9.7 μm silicate feature. Shown for illustrative purposes is the observed ISM extinction curve (thin solid curve) with arbitrary scaling in the y-direction.