Transverse and longitudinal waves

We are all familiar with the adjectives "longitudinal" and "transverse". And not just familiar, but actively use them in everyday life. But when it comes to waves, no matter what - in liquid, air, solid matter or electromagnetic fields, then a number of questions often arise. Usually, when hearing the words "transverse and longitudinal waves", the average person represents a sinusoid. Indeed, the vibrational perturbations on the water just look that way, so life experience gives just such a clue. In fact, the world is more complex and diverse: it contains both longitudinal waves and transverse waves.

If oscillations arise in any medium (field, gas, liquid, solid matter), transferring energy from one point to another with a velocity that depends on the properties of the medium itself, they are called waves. Due to the fact that the oscillations do not spread instantly, the phases of the wave at the starting point and some finite as they move away from the source are increasingly different. An important point that should always be remembered: when energy is transferred through vibrations, the particles that make up the medium do not move, but remain in their balanced positions. Moreover, if we consider the process in more detail, it becomes clear that not single particles are vibrating, but their groups concentrated in any unit of volume. This can be illustrated by the example of an ordinary rope: if one of its ends is fixed, and from the other produces wave-like motions (in any plane), then the waves appear, the rope material does not collapse, which would occur when the particles move in its structure.

Longitudinal waves are characteristic only of gaseous and liquid media, but transverse waves are also characteristic of solid bodies. At present, the existing classification divides all vibrational disturbances into three groups: electromagnetic, liquid and elastic. The latter, as you might guess from the name, are inherent in elastic (hard) environments, so they are sometimes called mechanical.

Longitudinal waves arise when the particles of the medium oscillate, being oriented along the propagation vector of the perturbation. An example is the impact on the butt of the metal rod by a dense, massive object. Transverse waves propagate in a direction perpendicular to the direction of the action vector. The natural question: "Why can only longitudinal waves appear in gases and liquid media"? The explanation is simple: the reason for this is that the particles that make up the data of the medium can move freely, since they are not rigidly fixed, in contrast to solids. Accordingly, transverse oscillations are fundamentally impossible.

The foregoing can be formulated a little differently: if in a medium the deformation caused by the disturbance manifests itself in the form of shear, stretching and contraction, then it is a solid body, for which both longitudinal and transverse waves are possible. If the appearance of a shift is impossible, then the medium can be any.

Of particular interest are longitudinal electromagnetic waves (SEW). Although theoretically nothing prevents the emergence of such fluctuations, official science denies their existence in a natural environment. The reason, as always, is simple: modern electrodynamics proceeds from the principle that electromagnetic waves can only be transverse. Refusal of such a worldview will entail the need to revise many fundamental beliefs. Despite this, there are many publications of the results of experiments that practically prove the existence of SEW. And this indirectly means the discovery of yet another state of matter, in which, in fact, generation of a given type of waves is possible.