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A light ray is a line or curve that is perpendicular to the light's wavefronts (and is therefore collinear with the wave vector). A slightly more rigorous definition of a light ray follows from Fermat's principle , which states that the path taken between two points by a ray of light is the path that can be traversed in the least time.
Polarization (waves) Coherence (physics), the quality of a wave to display a well defined phase relationship in different regions of its domain of definition; Hilbert transform, a method of changing phase by 90° Reflection phase shift, a phase change that happens when a wave is reflected off of a boundary from fast medium to slow medium
Sine waves occur often in physics, including wind waves, sound waves, and light waves, such as monochromatic radiation. In engineering , signal processing , and mathematics , Fourier analysis decomposes general functions into a sum of sine waves of various frequencies, relative phases, and magnitudes.
The wavelength of visible light waves varies between 400 and 700 nm, but the term "light" is also often applied to infrared (0.7–300 μm) and ultraviolet radiation (10–400 nm). The wave model can be used to make predictions about how an optical system will behave without requiring an explanation of what is "waving" in what medium.
Visulization of flux through differential area and solid angle. As always ^ is the unit normal to the incident surface A, = ^, and ^ is a unit vector in the direction of incident flux on the area element, θ is the angle between them.
Fermat's principle is most familiar, however, in the case of visible light: it is the link between geometrical optics, which describes certain optical phenomena in terms of rays, and the wave theory of light, which explains the same phenomena on the hypothesis that light consists of waves.
Caustics produced by a glass of water, visible as patches of light Cardioid caustic at the bottom of a teacup Caustics made by the surface of water Caustics in shallow water In optics , a caustic or caustic network [ 1 ] is the envelope of light rays which have been reflected or refracted by a curved surface or object, or the projection of that ...
Dispersion occurs when sinusoidal waves of different wavelengths have different propagation velocities, so that a wave packet of mixed wavelengths tends to spread out in space. The speed of a plane wave, , is a function of the wave's wavelength : = ().