# Wave optics

as wave optics one designates the subrange of the optics, which with the Wellennatur of the light concerns itself.

Light therefore consists of electrical and magnetic fields, which spread wavy (electromagnetic wave). With this model many characteristics of the light can be explained and also computed, which cannot be described by the geometrical optics. In addition belong color, interference, diffraction and polarization.

## history

already in 17. One recognized century that the classical interpretation of light as bundles of straight-line jets must be incomplete. Diffraction and interference thus cannot be explained. Christiaan Huygens noticed around 1650 that a light propagation would explain similar to water waves the phenomena. He formulated his Huygens principle, which means that from each point of a bending surface spherical elementary waves proceed, which overlay and cause so the observable diffraction effects. First Huygens was not seriously taken, since one favored the corpuscle theory of Isaac Newton. Only in 19. Century was confirmed the Wellentheorie by the double gap experiment by Thomas Young. The work of Joseph of Fraunhofer and Augustin Jean Fresnel removal the theory.

## characteristics of light waves

in the sense of the wave optics is light a transverse wave, i.e. the wave swings perpendicularly to their direction of propagation. One can characterize it by its wavelength , amplitude and phase.

### color and intensity

the color of the light correspond its wavelength. Monochromatic light has only one wavelength, while weisslicht represents an overlay of many waves of different wavelengths. The intensity of the light is proportionally to the amplitude of this wave, averaged over the time.

### coherency and interference

apart from the amplitude one can regard also the phase of the wave. If several waves stand in a constant phase relationship, then one speaks of coherency. Coherent waves have the characteristic that they can interfere with one another. Different waves overlay with the fact in such a way that it to the reinforcement (wave mountain meets destructive interference on wave mountain - constructional interference) or weakening (wave mountain meets on wave valley -) comes.

### polarization

a transverse wave swings always perpendicularly to the direction of the light propagation, has however still two degrees of freedom. If the oscillation takes place only in one level or if it changes regularly, then one speaks of polarized light.

### wave fronts

place rays of light one regards the generalized concept of the wave front in the wave optics. A wave front is a surface, which combines points of same phase of different waves in itself. Rays of light stand always perpendicularly on the wave front.

## borders to the wave optics

gives phenomena, which cannot be explained by the Wellentheorie. In addition from William the resounding wax belongs 1887 discovered and from Albert Einstein 1905 explained outside photoelectric effect (Nobelpreis 1921). Einstein explained the reciprocal effect between light and subject with energy portions (light quantum hypothesis). One spoke then of wave particle dualism. The contradiction of waves and particles is today in modern quantum physics on a abstrakteren level dissolved.