[en] It is shown that the post maximum decline in optical light during the outburst of a normal classical nova is caused by a shift in the wave-length of maximum energy to the ultraviolet. The constant luminosity phase which was directly observed in Nova FH Ser 1970 may, therefore, be common to all novae regardless of speed class. This implies that all speed classes of novae have similar energy budgets and that it is the total energy involved in the outburst which produces the variation in the observed characteristics of the novae. Recent thermonuclear runaway models for the outburst also show an extended period of high luminosity and high effective temperature following the initial outburst. (author)