B.1. Frequency Grid
The frequency grid consists of 89 points, ranging from 0.0944 to 5000 µm. Since, Draine & Lee (1984) give dust properties only upto 1000 µm, a power law extrapolation has been done beyond 1000 µm, upto 5000 µm. The frequency grid is not uniform and has been made finer within the wavebands of each of the ISOPHOT filters used in the present study.