Introduction. A wave is the transmission of energy without displacement of matter. It is a disturbance or agitation that moves in a certain environment and that, after passing, leaves it in its initial state. This mechanism covers a wide range of situations: From waves on the surface of a liquid to light, which is itself a type of wave. For thousands of years, waves have been the object of study. It all started when Pythagoras discovered that acoustic research was related to the theory of waves, since the strings of musical instruments generated sounds. Later, Galileo Galilei was able to relate the connection between vibratory bodies and different sounds, for which he used a pendulum, thus reaching the basic principles of MAS. Many other scientists continued their analysis, an example was Robert, who tested the theory that it is not possible for sound to travel in a vacuum, confirming that this type of wave travels in media such as air; Jean Le Rond d ’Alembert also contributed his grain of sand, deriving the equation of the wave. From now on future generations are dedicated to the study of this phenomenon. Christian Huygens, in the 18th century, made a wave theory of the nature of light, deducing, some time later, that every luminous object generates a disturbance in the ether. This last experiment formed the basis for the current definition of electromagnetic wave as the form of propagation of electromagnetic radiation through space. Objective. Analyze the transmission and reflection processes of traveling waves at an interface between elastic propagation media with different densities, emphasizing the phenomenon of phase inversion by reflection and the conditions for it to occur. Methodology. For this, it was necessary to emphasize different concepts, such as wave, mechanical wave, traveling wave, wave motion, reflection of a traveling wave, among others. Results. All waves, regardless of their class or propagation medium, have common properties that are clearly manifested in space, passing from one medium to another with different characteristics, the same ones that will be of vital importance for the changes in speed and direction that it undergoes. the wave disturbance at the interface, so that according to the characteristics of the medium a change in some of its properties will result in the wave motion changing irremediable. Conclusions. The waves were classified according to various criteria, as well as the main elements that describe it. It was shown that when a wave changes from one medium to another, it is reflected and depending on the boundary conditions that limit it, this reflection will be inverted or not. The law of reflection for plane waves and diffraction in circular waves was also studied. Consequently, the superposition principle was explained, which addresses the resulting wave function obtained through the sum of two completely individual waves that overlap.