In optics and telecommunication, the term optical path length has the following meanings:
- In a medium of constant refractive index, n, the product of the geometric distance and the refractive index.
- In a medium of varying refractive index, the integral of n δs, where δs is an element of length along the path, and n is the local refractive index.
Note: Optical path length is proportional to the phase shift that a lightwave undergoes along a path.
Fermat's principle states that the path light takes between two points is the optical path length index of refraction glass path that has the minimum optical path length.
Source: from Federal Standard 1037C and from MIL-STD-188
Electronics Topics
The field of electronics is the study and use of systems that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. The design and construction of electronic circuits to solve practical problems is part of the fields of electronic engineering, and the hardware design side of computer engineering. The study of new semiconductor devices and their technology is sometimes considered as a branch of physics.
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