BEHAVIOR OF EXTRAORDINARY RAYS IN UNIAXIAL CRYSTALS

We have experimentally investigated the behavior of extraordinary rays (E rays) in uniaxial crystals for two cases: that in which optical ax es are parallel to the surfaces and that in which they are inclined. T he E ray always rotates around the ordinary ray (O ray) in the same di rection that the crystal rotates around its surface normal. For the ca se when the axes are parallel to the surface, we discovered that the E ray rotates up to alpha = 2pi as the crystal rotates to phi = pi. The E ray traces a series of ellipses as the angle of incidence is varied . Snell's law is valid for the E ray only when the optical axes are pe rpendicular to the plane of incidence. For the case in which the optic al axes are incident, the E ray and the crystal rotate at different sp eeds except for the case of normal incidence. The speed of rotation in creases with the incidence angle. The ray traces a curve known as the Pascal worm, which is described by the equation (x2 + z2 - mx)2 = n2(x 2 + z2). When the optical axes coincide with the plane of incidence, t he space between the rays in the plane is not related to the angle of incidence.