Ray 3 : An elemental path of radiated engery; or the energy following this path. It is perpendicular to the phase fronts of the radiation. In tsunami wave refraction, an orthogonal
Intergovernmental Oceanographic Commission IOC technical series 37, Tsunami Glossary (A glossary of terms and acronyms used in the tsunami literature - English), , United Nations Educational, Scientific and Cultural Organization UNESCO, Paris, France 1991. http://unesdoc.unesco.org/images/0008/000885/08853 8eb.pdf, (ND/ Tsunami Sci - Brit) {590}