Fresneldiffraktio

Fresnel-diffraktio, also known as Fresnel diffraction or near-field diffraction, is a phenomenon that occurs when light waves bend around the edges of an opaque object or pass through an aperture. It is a type of diffractive optics that describes the wave pattern of light in the region close to the diffracting object, where the wave can be considered to be approximately spherical. This is in contrast to Fraunhofer diffraction, which occurs in the far-field where the wavefronts are approximately planar.

The Fresnel diffraction pattern is characterized by its dependence on the distance from the diffracting object. As the observation point moves further away from the object, the diffraction pattern changes. This is because the path difference between the light rays arriving at the observation point from different parts of the diffracting object varies with distance. The pattern is typically observed as a series of bright and dark fringes.

To analyze Fresnel diffraction, the Fresnel integrals are used. These integrals describe the amplitude and phase of the diffracted light wave. The theory of Fresnel diffraction is often developed using Huygens' principle, which states that every point on a wavefront can be considered a source of secondary spherical wavelets. The superposition of these wavelets then determines the wave pattern at a later time.

Key features of Fresnel diffraction include the spreading of light beyond the geometrical shadow of the obstacle and the formation of complex interference patterns. This type of diffraction is important in understanding phenomena such as the diffraction of light from small apertures and the behavior of light in optical systems when the observation distance is not very large compared to the size of the diffracting element. It finds applications in various fields of optics and wave physics.