  In this paper we present the revised view on the optical activity of crystals
based on the model of two dumped coupled oscillators. The results are compared
with the results of the same problem solved before and it is presented that the
results of the quantum mechanical model are the generalization of the classical
model only and they do not introduce the new terms of quantum mechanical
nature. The results are discussed with regard to the rotational strengths of
normal modes of vibrations and the formula for the complex rotatory power
containing the rotational strengths is presented.
