ABSTRACT A simple and novel technique has been employed to determine the birefringence in liquid crystalline phases such as nematic and smectic-A. The birefringence has been measured as phase angle between the light wave passing through the liquid crystal and the direct reference wave. The technique employed is the rotating Polaroid method. This technique can be directly used to harness the phase transition temperatures across different liquid crystalline phases as measured through the voltage output difference between the two waves which can be measured as lock-in output. The indigenously fabricated equipment was tested using standard samples. The phase transition temperatures of two well known and widely studied nO.m compounds viz., N-(p-n-butoxy/pentyloxy benzylidene)-p-n-methyl anilines (4O.2 and 5O.2) are measured. The transition temperatures obtained through this technique agree with those reported from differential scanning calorimeter technique, thermal microscopy and other techniques. The resolution observed was better than the other methods. The importance of this method is the study of dynamic variation of refractive index with temperature by the measurement of electrical signal output from the Lock- in amplifier.. This was confirmed by the determination of variation of refractive index of Methanol, Rhodamin 6G and Rhodamin B in Methanol with temperature, determined by some other advanced method1. The observed results are in better agreement than the results of reference-1. Ref:1 Turk J Phys 26 (2002) , 41 { 47. c TšUB_ITAK Experimental Investigation of Temperature Effect on the Refractive Index of Dye Laser Liquids S_. YALTKAYA University of Akdeniz, Faculty of Science and Arts, Department of Physics, Antalya-TURKEY e-mail: seref@pascal.sci.akdeniz.edu.tr R. AYDIN Middle East Technical University, Faculty of Science and Arts, Department of Physics, Ankara-TURKEY Other Authors: #Mrs.M.Rama Jyotsna, M.Sc., Research Scholor.

@Prof.V.G.KM.Pisipati, Retd., Professor of Physics, Acharya Nagarjuna University, Nagarjuna Nagar-522 510.