![]() ![]() In optics, Fraunhofer diffraction (named after Joseph von Fraunhofer), or far-field diffraction, is a form of wave diffraction that occurs when field waves are passed through an aperture or slit causing only the size of an observed aperture image to change due to the far-field location of observation and the increasingly planar nature of outgoing diffracted waves passing through the aperture. ReferenceĪpplications of Classical Physics by Roger D. This is why you commonly see Fraunhofer diffraction associated with the use of a lens, as a converging lens allows you to view this far field pattern much more practically. So that the Fraunhofer diffraction cannot be seen directly. We can estimate the relative phase difference from the point at the aperture's center and a point near its edge, namely It is the differences in the path length from the various parts of our aperture to a point of interest that lead to the interesting interference phenomenon associated with diffraction.Ĭonsider an aperture with a characteristic size $a$, and imagine trying to figure out the diffraction at a point roughly in line with the aperture at some distance $d$ from the point at the aperture's center. The intensity of light you see at any point is the contribution from all of the points at the aperture, where the contribution from any point decreases as the distance, and every contribution accumulates phase given its path. The reason people talk about two different kinds, is because there are two natural limits in a diffraction problem. You are right in that there is only one set of physical things going on in diffraction. ![]()
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