The transverse waves are those in which oscillation occurs in a direction perpendicular to the direction of wave propagation. On the contrary, longitudinal waves are waves in which the displacement through the medium occurs in the same direction as the displacement of the wave.
It should be remembered that waves propagate through a medium because of the vibration they cause in the particles in that medium. So, the propagation direction of a wave can be parallel or perpendicular to the direction in which the particles vibrate. Therefore, the distinction between transverse and longitudinal waves is marked.
The most typical example of a transverse wave is the circular waves that propagate on the surface of the water when a stone is thrown. Transverse waves are also electromagnetic waves, like light. As for electromagnetic waves, there is a particular case in which there is no particle vibration, as occurs in other waves.
Even so, they are transverse waves because the electric and magnetic fields associated with these waves are perpendicular to the direction in which the waves propagate. Other examples of transverse waves are waves transmitted along a string and S waves or secondary seismic waves.
Characteristics
Waves, whether transverse or longitudinal, have several characteristics that determine them. In general, the most important characteristics of a wave are as follows:
Wavelength (A)
It is defined as the distance between the furthest point on a wave and its equilibrium point. As a length, it is measured in units of length (usually measured in meters).
Wavelength (λ)
It is defined as the distance (usually measured in meters) covered by a disturbance in a given period of time.
This distance is measured, for example, between two successive crests (the crests are the farthest point from the equilibrium position at the top of the wave) or also between two valleys (the furthest point from the equilibrium position in the region). wave bottom) successive.
However, you can actually measure between two successive points on the wave that are on the same phase.
Period (T)
It is defined as the time (usually measured in seconds) it takes a wave to go through a complete cycle or an oscillation. It can also be defined as the time taken by a wave to travel a distance equivalent to its wavelength.
Frequency (f)
It is defined as the number of oscillations that occur in a unit of time, usually one second. So when time is measured in seconds (s), frequency is measured in Hertz (Hz). Frequency is usually calculated from the period using the following formula:
f = 1 / T
Wave propagation velocity (v)
It is the speed at which the wave travels (the energy of the wave) through a medium. It is usually measured in meters per second (m / s). For example, electromagnetic waves travel at the speed of light.
The propagation speed can be calculated from the wavelength and the period or frequency.
V = λ / T = λ f
Or simply dividing the distance covered by the wave in a given time:
v = s / t
Examples
Electromagnetic waves
Electromagnetic waves are the most important case of transverse waves. A particular feature of electromagnetic radiation is that, unlike mechanical waves that require a medium by which to propagate, they do not need a medium to propagate and can do so in a vacuum.
This does not mean that there are no electromagnetic waves moving through a mechanical (physical) medium. Some transverse waves are mechanical, as they require a physical medium for their propagation. These transverse mechanical waves are called T waves or shear waves.
Furthermore, as mentioned above, electromagnetic waves propagate at the speed of light, which in the case of a vacuum is on the order of 3 × 10 8 m / s.
An example of an electromagnetic wave is visible light, which is electromagnetic radiation whose wavelengths are between 400 and 700 nm.
Cross waves in water
A very typical and very graphic case of a transverse wave is one that occurs when a rock (or any other object) is dropped into water. When this occurs, circular waves are produced that propagate from where the stone impacted the water (or the wave’s focus).
Observing these waves allows us to appreciate how the direction of vibration that occurs in the water is perpendicular to the direction of wave movement.
This is best observed if a buoy is placed close to the point of impact. The buoy goes up and down vertically as the wavefronts arrive, which move horizontally.
More complicated is the movement of waves in the ocean. Their movement involves not only the study of transverse waves, but also the circulation of water currents as the waves pass. Therefore, the real movement of water in the seas and oceans cannot be reduced to just a simple harmonic movement.
wave on a rope
As mentioned earlier, another common case of a transverse wave is the displacement of a vibration by a string.
For these waves, the speed at which the wave travels through the taut string is determined by the tension of the string and the mass per unit length of the string. Thus, the wave velocity is calculated from the following expression:
V = (T / m / L) 1/2
In this equation, T is the tension of the string, m its mass, and L is the length of the string.
