and \[fig:hmd785\]d). The hydrodynamic model D07 agrees fairly well with the observed bolometric light curve, but the relevant atmosphere model fails to reproduce the H$\alpha$ profile observed in SN 1999em. We thus conclude that the short distance of 7.85 Mpc should be discarded.

Development of the optimal model {#sec:devmod}
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Although the major issues of light curve theory were recognized a long time ago (Grassberg et al. [@gin71]; Falk & Arnett [@fa77]), it is useful to consider an SN outburst in a more detailed approach. This study of SN 1999em provides a good opportunity to examine the time development of a normal SN IIP. Figures \[fig:snphs\] and \[fig:swbrck\]a show the following stages in the observer time scale: a shock breakout ($t_{obs} \le t_1$), an adiabatic cooling phase ($t_1 < t_{obs} \le t_2$), a phase of cooling and recombination wave (CRW) ($t_2 < t_{obs} \le t_3$), a phase of radiative diffusion cooling ($t_3 < t_{obs} \le t_4$), an exhaustion of radiation energy ($t_4 < t_{obs} \le t_5$), a plateau tail ($t_5 < t_{obs} \le t_6$), and a radioactive tail ($t_{obs} > t_6$). In addition to the above stages there are two specific points: a transition from acceleration of the envelope matter 