Diffraction . Term that comes from the Latin diffractus which means broken. The etymology refers to the phenomenon by which a wave can contour an obstacle in its propagation, moving away from the behavior of rectilinear rays.


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The evolution of a wave follows the laws imposed by the D’Alembert equation that determines the diffraction phenomena. In the case of monochromatic waves (any wave can be considered a superposition of monochromatic waves), this equation becomes the Helmholtz equation, which is based on the process of calculating the amplitude of a wave field that in its propagation you encounter one or more obstacles.


Diffraction, in physics , is the phenomenon of wave motion in which a wave of any type spreads after passing along the edge of a solid object or passing through a narrow slit, rather than following its advance in a straight line.

Diffraction is only observed if the obstacle encountered by the waves is of the same order as the wavelength of the movement since when it is greater, the waves follow the rectilinear propagation.

The expansion of light by diffraction causes a blur that limits the useful magnification capacity of a microscope or telescope . For example, details less than half a thousandth of a millimeter cannot be seen on most light microscopes. Only a scanning optical microscope near field may exceed the diffraction limit and display slightly less detail than the length of the light wave.

Diffraction Experiment

The distribution and distance between the maxima and minima of a diffraction diagram inform about the distance and distribution of the grid nodes. In this experiment, red light from a laser is passed through a slide on which several grids are drawn (Figure 30). The wavelength of the red light used is 670 nm.

The first part of the experiment consists of observing the symmetry of the grid affected by the distribution of the light spots on the diffraction diagram. In the second part, the distance between the points on one of the grids (the first one in figure 3) is determined and the distance between points is measured in the diffraction diagram.

If in a similar experience the slide is replaced by the grids formed by the atoms of a crystal , and the laser by an X-ray source , whose wavelength is the order of the different interatomics (about Ȧ), it could be determined, from the obtained diffraction diagram, the position of the atoms in the crystal. This is the basis of the determination of crystalline structures by x-ray diffraction, one of the most important techniques in current chemistry .


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