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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 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.
The simplest type of birefringence is described as uniaxial, meaning that there is a single direction governing the optical anisotropy whereby all directions perpendicular to it (or at a given angle to it) are optically equivalent. Thus rotating the material around this axis does not change its optical behaviour.
Following his remarks on the propagation medium and the speed of light, Huygens gives a geometric illustration of the wavefront, the foundation of what became known as Huygens’ Principle. His principle of propagation is a demonstration of how a wave of light (or rather a pulse) emanating from a point also results in smaller wavelets: [12]
The Hamilton optico-mechanical analogy is closely related to Fermat's principle and thus to the Huygens–Fresnel principle. [10] Fermat's principle states that the rays between wavefronts will take the path least time; the concept of successive wavefronts derives from Huygens principle.
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.
Treating a point on the path as a source is the minimum requirement of Huygens' principle, and is part of the explanation of Fermat's principle. But it can also be shown that the geometric construction by which Huygens tried to apply his own principle (as distinct from the principle itself) is simply an invocation of Fermat's principle. [4]
Notation for calculating the wave amplitude at point P 1 from a spherical point source at P 0.. At the heart of Fresnel's wave theory is the Huygens–Fresnel principle, which states that every unobstructed point of a wavefront becomes the source of a secondary spherical wavelet and that the amplitude of the optical field E at a point on the screen is given by the superposition of all those ...