Refraction - the simplest case

At longer ranges of outdoor sound propagation, refraction due to temperature and wind variations results in ray paths that are curved. Under the assumptions of the linear effective sound speed and nearly horizontal propagation, the ray path in the form of parabola is used. The shape of the ray and the position of the shadow zone, in the presence of a negative gradient, is studied. In the converse case of a positive gradient, the analysis of the additional reflected rays is performed. This is the most simple case of the theory of refraction.