Temperature Dependence of Birefringence in Liquid Crystals

The temperature dependence of birefringence in the liquid crystal methoxybenzylidene-$n$-butylaniline has been obtained by measuring the birefringence of a thin sample placed between crossed polarizers. Measurements of transmitted laser light yield minima and maxima which can be related to the difference in refractive indices. A converging beam displays the orientation of the optic axis and is used in determining $\Delta n$. Wavelength dependence is measured in a similar way using white light and spectrograph.