  We explore the effect of varying the spectral energy distribution of the
incident continuum, by simultaneously and self-consistently computing the
structure of an H II region and a photodissociation region that are in pressure
equilibrium. The results of the calculations are applied to extragalactic
observations. The intensity ratio diagrams of far-infrared (FIR) emission for
Herschel bands (70, 110, 160, 250, 350, and 500 {\mu}m) and the contribution
from H II regions for these specific FIR emissions are presented for the first
time. With these diagrams, we compare the predicted FIR continuum intensity
ratios of M82 with observations by Herschel.
