INTERFEROMETRIC STUDIES ON NATURAL AND INDUCED BIREFRINGENCE

Abstract

When light passes through all transparent crystals except for those belonging to the cubic system, it splits into two rays propagating with different velocities in different directions. This phenomenon is called double refraction or birefringence. External action may cause double refraction to appear in transparent amorphous crystals, and also in crystals of cubic system. This occurs in particular, upon the mechanical deformations of materials. The induced birefringence produced is proportional to the stress at a given point of a sample (i.e., to the force per unit area). In the first chapter we defined the birefringence phenomenon, its reasons and the propagation of light in the birefringent crystals, then we mentioned the previous works that appeared in this field. In the second chapter we measured the birefringence and its dispersion for Fortepan photographic plate of cellulose and Muscovite mica sheet. We also evaluated the birefringence for cellophane sheet by using a simple interferometric technique. In the third chapter an interferometric method has been used to investigate the effect of controlled stress on transparent materials such as plastic and glass. As a result we evaluated Young's modulus and the stress