# wave propagation

When falling on the surface of the water, a stone displaces a certain volume of this substance, which projects both laterally and vertically.

Let’s imagine a rope stretched and very long. If we shake one of its ends, we will see that the wave formed reaches the other end without any point on the string having undergone lateral displacement. If we place a tape at any point between the two ends of the string, we will see that, with the passage of the oscillation, the tape will make an up and down movement, thus describing an MHS, without being transported by the disturbance.

This disturbance that propagates along a string is called a **wave** . A fundamental characteristic of **wave propagation** is:

*Waves transport energy without transporting matter* .

We classify wave propagation based on the following criteria: direction of vibration, nature of vibration and degrees of freedom for wave propagation.

*vibration direction*

– transverse propagation: when the vibration direction is perpendicular to the wave propagation direction.

– Longitudinal propagation: it is the one in which the vibration direction is the same as the wave propagation.

– Mixed propagation: it is that propagation where both previous situations occur, simultaneously.

*nature of vibration*

In mechanical propagations, that is, in mechanical waves, there is transport of mechanical vibrations, that is, it is the particles that vibrate. Mechanical propagation is present in strings, springs, on the surface and in the interior of liquids, etc. Therefore, mechanical waves need a medium to propagate.

Electromagnetic waves correspond to variations in electric and magnetic fields, caused by oscillating electric charges. This is the case with radio waves, microwaves, X-rays, etc. Electromagnetic waves, unlike mechanical waves, do not require a propagation medium.

*Degrees of freedom of propagation*

In one-dimensional propagation, waves travel along a line. In two-dimensional propagation, waves are produced on a surface. And in three-dimensional propagation, waves propagate in all directions, throughout space.