  The optical activity of a chiral medium is discussed from the view point of
transfer of energy. The absorbed energy of the polarized light in the optical
active medium is transferred to the mechanical rotation of the chiral molecule.
They acquire the helicity dependent geometric phase due to passage of the
polarized light which loses energy by having an optical rotation. The
entanglement of a polarized photon and fermion is the very source of this
behavior. This theoretical knowledge has been reflected in an experimental
study with six essential and five non-essential amino acids.
