Question

Using Huygens'* principle, construct the wavefronts and the propagation directions of the ordinary and extraordinary rays in a positive uniaxial crystal whose optical axis

(a) is perpendicular to the incidence plane and parallel to the surface of the crystal;

(b) **** in the incidence plane and is parallel to the surface of the crystal;

(c) **** in the incidence plane at an angle of 45° to the surface of the crystal, and light falls at right angles to the optical axis.

Answer 1

The wave surface of a uniaxial crystal consists of two sheets of which one is a sphere while the other is an ellipsoid of revolution.

*The optic axis is the line joining the points of contact. To makes the appropriate Huyghen’ construction we must draw the relevant section of the wave surface inside the crystal and determine the directions of the ordinary and extraordinary rays.The result is as shown in Fig. 42 (a, b & c) of the answers.**