In addition to the phenomenon of interference, presented in the previous section, the waves present a wide range of behavior in different situations. The main ones are presented below.

Reflection

It is when the wave strikes a surface of separation between two media and returns to the same medium.

Reflection of a one-dimensional mechanical wave.
  • a) On the left part of the figure, we present what happens with a pulse wave which is being reflected by a fixed end of the rope (imagine that the rope is tied to a wooden trunk).
  • b) On the right part, this is what happens with a pulse reflected by an end that can move vertically (imagine that the rope is attached to a ring which can slide vertically on a wooden trunk).

The reflection of a mechanical wave at a fixed end is in reverse phase.

The reflection of a mechanical wave on the free end (mobile) occurs without phase inversion.

Refraction

It is the phenomenon that occurs when a wave comes from one medium and penetrates into another medium. (This phenomenon is addressed deeply in the section: Optic | Refraction and Refractive Means )

Phenomenon of refraction. The figure illustrates a wave (the lines represent the ridges of the wave) propagating in a fluid in a vessel. The dark blue color is a deeper region and the lighter a shallower region. The wave, when passing from one region to another, suffers a change in its speed, and therefore in their direction.

Diffraction

"Evading obstacles" and "Distinguishing particle from waves."

Diffraction is the distortion of linear propagation of waves that encounter obstacles, allowing the wave to circumvent them. The diffraction phenomenon is a characteristic of waves. Particles do not diffract.

Conditions of Sharp Perception

The diffraction phenomenon becomes increasingly clearer as the relationship between incident wavelength ( \(\lambda\) ) and the size of the orifice or barrier \(d\) becomes smaller than 1. $$ \text{sharpness} = \frac{\lambda}{d} $$

Application

Diffraction allows waves to bypass obstacles. Because of the diffraction it is possible to hear the sounds that are produced in a certain room from one house to another room.

Illustration of the diffraction phenomenon. The lines illustrate the peaks of waves that propagate in a fluid, the brown rectangles represent wooden obstacles. Depending on the position of the obstacles, the wave diffracts in different ways.

Polarization

It is a wave phenomenon typical of transverse waves. When this phenomenon occurs, the oscillations in the propagation medium are restricted to one plane.

Illustration of a light being polarized. When going through a polarizer, vertically, only the vertical oscillations (blue wave) are transmitted. Once polarized vertically, the light cannot pass through a horizontal polarizer. In this case, the final light intensity will depend on the angle between the polarizers.

Other Phenomena

There are many other interesting phenomena in the wave. Here we will list a few more.

Dispersion
It is the phenomenon through which a wave is decomposed into the set of its constituent single waves.
Attenuation
Effective reduction of the intensity of a wave, which crosses a medium material and interacts with it.
Resonance
Phenomenon that occurs when a oscillating system is excited by a periodic external agent with a frequency identical to one of its own frequencies. In these conditions the transfer of energy from the external source to the system is maximum.