View source for Frequency conservation law

Since according to E = const.  In the closed system the energy is preserved, one can also deduce the frequency conservation law.  Namely, E = h * f applies.  Since Plank's constant h is a constant, one divides an arbitrary but certain number const.  by a number when you put the two equations together.  This is again any arbitrary but specific number const.  So '''f = const.''' in the isolated system, the frequencies are retained.