Radiated energy per unit time (in solar luminosities) emitted by dust in the SN ejecta as a function of wavelengths, for nine different epochs (see Eq. (18)). The unattenuated luminosity (dashed line) corresponds to the total energy per unit time (from the dust), while the observable luminosity (solid line) is the luminosity that escapes the system, after taking the progressive escape probabilities into account, and will be the one that can be observed (see Sect. 4 and Eqs. (17) and (18) for details).