Refraction

Interruption or refraction means the change in the propagation direction of a wave due to a spatial variation of its speed of propagation, which is described specifically for the light waves by the refractive index n of a medium. Generally occurs a break in any kind of waves that propagate in more than one dimension, such as sound waves, water waves or seismic waves.

Refraction, unlike diffraction object of ray optics, which is valid for structures, which are large compared to the wavelength. By refraction at interfaces occurs at a bend in the beam, which is described by the law of refraction. In the continuous change in the propagation velocity jets are curved, see about astronomical refraction. In both cases, the Fermat's principle applies, according to which ray paths of extremal, usually minimal duration or length of use.

The dependence of the refraction on the wavelength ( ie in light of the color) is called dispersion.

Anisotropic materials are birefringent, that is, the proportions of a wave are different depending on their polarization (strongly ) broken.

Applications

Various forms of refraction of waves can be found in nature. These pictures show an example of the changes appearing form of a rod by light refraction after it is immersed in water. Therefore, it requires some practice to take fish from the surface of the water.

After Zufüllen of water, the rod appears bent slightly upward.

Comparison of the two images ( overlay ).

Schematic representation showing the effect of the ' optical lift '

The refraction of electromagnetic waves and especially the light has great importance in the technical optics. It determines the function of prisms and lenses.

At transitions between materials of different acoustic velocity seismic waves are refracted in a characteristic manner. Therefore, geophysicists use of the refraction of waves caused by earthquakes, to gain knowledge about the structure of Earth's interior.

History of description and exploration

• See also Snell's law of refraction
• And Fermat's principle