The etymology from diffraction refers us to diffractus, a term that can be translated as "broken" . This concept is used in the field of physical to name the deflection of a wave when it crosses an opening or hits the edge of an opaque element .
Diffraction is a phenomenon that involves all waves : electromagnetic, radio, sound, etc., and it is possible to predict its development using different mathematical approaches. When the wave crosses a crack or encounters an obstacle, it deviates.
There is method called analysis Huygens principle , which allows us to understand diffraction as a wavefront that is seen as a series of emitters capable of redirecting the wave when it oscillates and thus promote it to propagate. Although the waves produced by the oscillators are spherical, their interference causes a flat wave that moves in the same direction as the initial one.
The near field diffraction , also known as from Fresnel (by Augustin-Jean Fresnel , a French physicist born in 1788 and died in 1827), is a Pattern of diffraction of those electromagnetic waves that are obtained in the vicinity of the element that causes the phenomenon itself, which is usually an opening or a source.
In the field of optics, the branch of physics that studies the properties and behavior of light is known as opening to a hole or hole through which the light passes. Said in more specific terms, it is the determining factor of the angle that the cone of the ray beam will have to focus on the plane.
Another of the concepts that are key to understanding and calculating the diffraction of the near field is the fresnel number , another of the contributions of the respected French physicist. It's about a number which is not defined by physical units (that is, a dimensionless number or pure), used in the field of optics and defined by means of the following equation: Square opening / Distance between the opening and the screen x Wavelength .
The from the far field or from Fraunhofer instead, it is oriented to a wave whose source and its screen is very far from the obstacle that causes diffraction, so that on these two plane waves (also called monodimensional, are constant and their wave fronts are parallel and normal to the phase velocity).
It is correct to say that far field diffraction is a particular case of the previous one. his analysis it is easier, since the distance between the opening and the screen is considerable and it is possible to study the rays in parallel, something that does not happen with the diffraction of the near field.
Thanks to the use of the Fresnel number it is possible to know to which of the two types of diffraction we are: when your value It is much lower than unity, the present phenomenon is the diffraction of the far field, and vice versa.
The phenomenon of diffraction is applied in different types of studies and research. The call X-ray crystallography It is based on diffraction to analyze materials with periodic structure, such as crystals . This technique was very important in the study of DNA structure , for example.
In this case, the X-rays they experience diffraction due to the electrons that are surrounding the atoms of the crystal The beam that emerges from this encounter harbors data on the types of atoms and their positions. This information is observed and measured through different detectors.