Absorption efficiencies for four materials and a range of wavelengths and grain sizes. Wavelength are separated by factors of 10, the longest wavelengths are labelled. Solid lines indicate Mie results, dashed lines the small-grain asymptote given in Eq. (12). The upper boundaries of the light-shaded regions are defined by Eq. (13), the left boundaries by Eq. (15). Black dotted lines follow Eq. (13) multiplied by an additional factor n to roughly trace the actual smoothed Q_abs. Values are given for stellar luminosity L = L_Sun and a distance r = 100 au.