Diffraction, in physics, is the phenomenon of wave motion in which a wave of any kind extends after passing along the edge of a solid object or through a narrow slit, instead of moving forward in a straight line.

The 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 produces a blur that limits the useful magnification capacity of a microscope or telescope. For example, details smaller than half a thousandth of a millimeter cannot be seen in most optical microscopes.

Only a near-field scanning optical microscope can exceed the diffraction limit and display details slightly smaller than the wavelength of light.

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DichotomyDiffraction (reticulum of)