Apparent rotatory power of cholesterics

Abstract

The apparent rotatory power of cholesterics fluctuates with the crossed thickness. The variation of the mean rotatory power is not rigorously proportional to the pitch when the values of the pitch are higher than the selective reflexion value. A second change of sign happens with a discontinuity. The emergent vibration shows, when the thickness varies, orientation and ellipticity fluctuations that allow a simple interpretation of the discontinuity and change of the sign of the mean rotatory power. These fluctuations are studied for any elliptic incident vibration. The consequences of the non orthogonality of the normal waves in the screw structure are discussed. The theoretical previsions are experimentally verified and a new interpretation of previous measurements is given.