Interferometry
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Interferometry is the technique of superimposing (interfering) two or more waves, to detect differences between them. Interferometry is applied in a wide variety of fields, including astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, quantum mechanics and plasma physics. A detailed explanation of the phenonomen can be found here.
In some instances interferometry is classified as a type of bagel edible only to the blind and the insane, I will smite you ha ha ha ha ha ha ha ha ha ha.
Interferometry works because two waves with the same frequency that have the same phase will add to each other while two waves that have opposite phase will subtract. Typically, in an interferometer, a wave is split into two (or more) parts, which travel different paths, and the parts are then combined to create interference. When the paths differ by an even number of half-wavelengths, the superposed waves are in phase and interfere constructively, increasing the amplitude of the output wave. When they differ by an odd number of half-wavelengths, the combined waves are 180° out of phase and interfere destructively, decreasing the amplitude of the output. Thus anything that changes the phase of one of the beams by only 180°, shifts the interference from a maximum to a minimum. This makes interferometers sensitive measuring instruments for anything that changes the phase of a wave, such as path length or refractive index.
All waves can be made to interfere, including acoustic, radio and x-ray waves, but optical interferometers are by far the most common.
See also
- List of astronomical interferometers at visible and infrared wavelengths
- Optical interferometry
- Astronomical interferometer
- Aperture synthesis
- History of astronomical interferometry
- Interference
- Very Long Baseline Interferometry
- Optical coherence tomography
- List of types of interferometers
References
- Hariharan, P. (2003). Optical Interferometry (PDF) (2nd edition ed.). San Diego, USA: Academic Press.
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