On the frequency dependence of ultrasonically induced birefringence in isotropic phase of liquid crystal: 5CB (p-n-pentyl p'-cyanobiphenyl)

Theoretical expressions for the ultrasonically induced birefringence of liquids are obtained in the frame work of de Gennes’ phenomenological theory. The intensity and frequency dependence of ultrasonically induced birefringence in the isotropic phase of p-n-pentyl p′-cyanobiphenyl (5CB) was measured in order to examine the usefulness of birefringence measurements for investigating dynamical properties liquids. The observed birefringence was proportional to the square root of ultrasonic intensity. The birefringence divided by the square root of ultrasonic intensity increases with increasing frequency and appears to saturate when the ultrasonic frequency approaches the relaxation frequency of molecular reorientation. The observed values of birefringence were reproduced satisfactorily by the expression derived in this paper.

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