The mild-slope equation is a mathematical representation used in coastal engineering and fluid dynamics to describe the propagation of surface water waves over varying bathymetry (the underwater equivalent of topography). It is especially useful for analyzing wave behavior in coastal areas, where the depth of the water changes gradually.

The Schamel equation is a type of nonlinear partial differential equation that is often used in plasma physics and fluid dynamics to model the evolution of wave phenomena, especially in the context of plasma waves and solitary waves. It is derived from the Korteweg-de Vries (KdV) equation and often appears in studies involving solitons and other wave solutions in dispersive media.

Washburn's equation describes the capillary action of liquids in porous media or thin tubes. It quantifies the rate at which a liquid will diffuse into a porous material due to capillary forces. The equation is often used in the context of materials science, fluid mechanics, and petroleum engineering, among other fields.

Gauss's law is a fundamental principle in electrostatics, part of Maxwell's equations, that relates the electric field generated by a charge distribution to the charge enclosed within a closed surface.

The Doppler effect is a phenomenon observed when the source of a wave (such as sound or light) is moving relative to an observer. It describes the change in frequency (or wavelength) of the wave as perceived by the observer due to the relative motion. 1. **Sound Waves**: When a sound source moves towards an observer, the sound waves get compressed, resulting in a higher frequency (or pitch) of the sound.

The K correction is a term used in astronomy to refer to a mathematical adjustment applied to the observed brightness (or luminosity) of astronomical objects, such as stars or galaxies, to account for the effects of redshift and to enable a more accurate comparison of their intrinsic properties. When light from distant objects is observed, the light waves are stretched due to the expansion of the universe, a phenomenon known as redshift.

A Laser Doppler Vibrometer (LDV) is an optical device used to measure vibrations or oscillations of an object without any physical contact. It operates on the principle of the Doppler effect, where the frequency of light reflected off a moving surface changes according to the velocity of that surface.

The relativistic Doppler effect refers to the change in frequency (and corresponding wavelength) of light or other waves emitted by a source that is moving relative to an observer, taking into account the principles of Einstein's theory of relativity. This effect becomes significant at speeds that are a substantial fraction of the speed of light.

A 22° halo is a type of optical phenomenon that appears as a ring of light encircling the sun or, less commonly, the moon. It is characterized by a radius of approximately 22 degrees from the center of the light source. This phenomenon occurs due to the refraction, reflection, and dispersion of light through ice crystal prisms in the atmosphere, typically found in cirrus or cirrostratus clouds.

The parhelic circle is an optical phenomenon related to the scattering of sunlight in the atmosphere, often associated with various types of halos. It appears as a horizontal circle that runs parallel to the horizon and is typically seen at the altitude of the observer's eye. The parhelic circle is most commonly observed when there are ice crystals in the atmosphere, such as in cirrus clouds.