  We study the evolution of the normalized flux of selected ultraviolet
emission lines of three classical novae (PW Vul, V1668 Cyg and V1974 Cyg).
Different phases ofthe outbursts are studied. We attribute the spectral
behavior of the three systems to the variation of the optical thickness and
temperature of the envelope during the different phases of the outbursts. Our
results are consistent with the theoretical models of classical novae. We also
present optical photometric observations of the three systems in the post-novae
phase. These observations show the variation of the light curves of these
systems and the different times of maxima and minima.
