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Gauging pressure with light: the fixed-length optical cavity

To measure pressure, the FLOC detects subtle differences in light passing through two channels, one flooded with gas and the other in vacuum. At either end of each channel is a semi-reflective mirror. Laser light enters the channels through one side and reflects back and forth between the mirrors, forming standing waves. Some of this light exits the channels through the other side. The presence of gas in the top channel causes the wavelength to shorten. When the light from the two channels is combined, it creates a wave pattern, a signal that can be used to calculate the gas's pressure in real time. Music credit: Readers! Do You Read? by Chris Zabriskie (CC-BY)

February 2019 • NIST • • Tagged: Animation