Translations:Wavefronts and raypaths/4/en

In Figure 2, the radii SA, SB, and SC are three of the raypaths associated with the spherical wavefronts. They can be given physical significance by thinking of them as the paths over which the energy of the disturbance travels from the source S to any wavefront or from any wavefront to a later one. It is evident in this simple case that the raypaths are everywhere at right angles to the wavefronts. This geometry (that is, the orthogonality of raypaths and wavefronts) is true for any isotropic medium whether the medium is homogeneous or not.