Definition of Ray (1/2) Given a propagating wave,every curve that is everywhere perpendicular to the wavefront is called electromagnetic ray.A ray is the path of the wavefront.There is a mutual identification btw wave and ray Therefore we assume that the ray also has a field,the field of the wave at every point Definition of Ray (1/2) • Given a propagating wave, every curve that is everywhere perpendicular to the wavefront is called electromagnetic ray. A ray is the path of the wavefront. There is a mutual identification btw wave and ray • Therefore we assume that the ray also has a field, the field of the wave at every point