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Huygens principle of double refraction, named after Dutch physicist Christiaan Huygens, explains the phenomenon of double refraction observed in uniaxial anisotropic material such as calcite. When unpolarized light propagates in such materials (along a direction different from the optical axis ), it splits into two different rays, known as ...
The Huygens–Fresnel principle (named after Dutch physicist Christiaan Huygens and French physicist Augustin-Jean Fresnel) states that every point on a wavefront is itself the source of spherical wavelets, and the secondary wavelets emanating from different points mutually interfere. [1] The sum of these spherical wavelets forms a new wavefront.
Treatise on Light: In Which Are Explained the Causes of That Which Occurs in Reflection & Refraction (French: Traité de la Lumière: Où sont expliquées les causes de ce qui luy arrive dans la reflexion & dans la refraction) is a book written by Dutch polymath Christiaan Huygens that was published in French in 1690.
Christiaan Huygens' construction. In his 1678 Traité de la Lumière, Christiaan Huygens showed how Snell's law of sines could be explained by, or derived from, the wave nature of light, using what we have come to call the Huygens–Fresnel principle.
Thus Huygens' construction and Fermat's principle are geometrically equivalent. [19] [Note 6] Through this equivalence, Fermat's principle sustains Huygens' construction and thence all the conclusions that Huygens was able to draw from that construction. In short, "The laws of geometrical optics may be derived from Fermat's principle". [20]
The Huygens–Fresnel principle is one such model; it states that each point on a wavefront generates a secondary wavelet, and that the disturbance at any subsequent point can be found by summing the contributions of the individual wavelets at that point.
The Huygens–Fresnel principle can be derived by integrating over a different closed surface (the boundary of some volume having an observation point P). The area A 1 above is replaced by a part of a wavefront (emitted from a P 0 ) at r 0 , which is the closest to the aperture, and a portion of a cone with a vertex at P 0 , which is labeled A ...
The principle yields an equivalent problem for a radiation problem by introducing an imaginary closed surface and fictitious surface current densities.It is an extension of Huygens–Fresnel principle, which describes each point on a wavefront as a spherical wave source.