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What is interferometry?
Interferometry is the branch of science devoted to studying and measuring the interaction of waves, including light waves, seismic waves, ocean waves, and sound waves.

How does it work?
Interference occurs when two waves come together at the same time and place. Dissonance, resonance, beat frequency, and hetrodyning are all interference phenomena. Interferometry involves using these interference phenomena for measurement purposes, either for very small angles or for tiny distance increments.

An interferometer is the device used to make these measurements. There are many different types of interferometers, but each essentially operates on the same basic premise. A beam of light emerges from a single source (e.g., a laser or lamp), and two or more flat mirrors are used to split the single beam into multiple beams. These beams are then combined so as to interfere with each other, and users will then look for alternating bands of light and dark light, called fringes. Fringes are bright where the beams are linearly adding together and dark where they are canceling each other out. Moving either mirror along the optical axis will cause the fringes to shift an equal amount in lockstep. Counting the number of fringes (one wavelength at a time) will determine the measurement of this movement.

What are its advantages?
•• Extremely precise
•• Very sensitive
•• Relatively quick, simple process

What's Interferometry used for?
•• Radio astronomy
Detection of surface changes
•• Generating digital elevation maps
•• Identifying sites of massive star formation and directly measuring distances to galaxies
•• Determining three dimensional motions in space
•• Pinpointing land surface changes (e.g., those created by earthquakes or landslides)

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