This paper presents a study of the spectral energy distributions (SEDs) of T Tauri stars with passive circumstellar disks. The authors model the disks as passive reprocessing systems, where the energy absorbed by the disk is re-emitted as infrared radiation. The disk is surrounded by a layer of superheated dust grains that re-emit about half of the absorbed stellar energy back into space, while the other half is directed inward, regulating the disk's interior temperature. The heated disk flares, absorbing more stellar radiation, especially at large radii, compared to a flat disk. The SED from the disk is relatively flat in the thermal infrared, with the surface layer contributing significantly more than the interior, especially at larger radii. Spectral features from the superheated dust layer appear in emission if the disk is viewed nearly face-on. The study compares the SEDs of flat and flared disks, finding that flared disks emit more power at mid-IR wavelengths than flat disks. The SEDs of flared disks show a gradual steepening of the spectral index beyond 300 microns as the disk becomes increasingly optically thin. The authors also consider the effects of radiative equilibrium and hydrostatic equilibrium on the disk structure and SEDs. They find that the temperature of the superheated dust layer is determined by radiative balance and is independent of the ambient gas temperature. The gas temperature is regulated by more subtle processes, and the disk's opacity is dominated by narrow, Doppler-broadened molecular lines. The study also addresses unresolved issues, such as the stability of disks in radiative and hydrostatic equilibrium, the dependence of the SED on disk inclination, the contribution of molecular lines to the thermally-emitted spectrum, and the effects of active accretion on the SEDs. The authors conclude that the SEDs of T Tauri stars with passive circumstellar disks can be well explained by the models presented, and that further observations and studies are needed to resolve the remaining questions.This paper presents a study of the spectral energy distributions (SEDs) of T Tauri stars with passive circumstellar disks. The authors model the disks as passive reprocessing systems, where the energy absorbed by the disk is re-emitted as infrared radiation. The disk is surrounded by a layer of superheated dust grains that re-emit about half of the absorbed stellar energy back into space, while the other half is directed inward, regulating the disk's interior temperature. The heated disk flares, absorbing more stellar radiation, especially at large radii, compared to a flat disk. The SED from the disk is relatively flat in the thermal infrared, with the surface layer contributing significantly more than the interior, especially at larger radii. Spectral features from the superheated dust layer appear in emission if the disk is viewed nearly face-on. The study compares the SEDs of flat and flared disks, finding that flared disks emit more power at mid-IR wavelengths than flat disks. The SEDs of flared disks show a gradual steepening of the spectral index beyond 300 microns as the disk becomes increasingly optically thin. The authors also consider the effects of radiative equilibrium and hydrostatic equilibrium on the disk structure and SEDs. They find that the temperature of the superheated dust layer is determined by radiative balance and is independent of the ambient gas temperature. The gas temperature is regulated by more subtle processes, and the disk's opacity is dominated by narrow, Doppler-broadened molecular lines. The study also addresses unresolved issues, such as the stability of disks in radiative and hydrostatic equilibrium, the dependence of the SED on disk inclination, the contribution of molecular lines to the thermally-emitted spectrum, and the effects of active accretion on the SEDs. The authors conclude that the SEDs of T Tauri stars with passive circumstellar disks can be well explained by the models presented, and that further observations and studies are needed to resolve the remaining questions.