CLAUS LUNAU / SCIENCE PHOTO LIBRARY CLAUS LUNAU / SCIENCE PHOTO LIBRARY
Seismometer. Illustration of a type of seismometer, a device used to record the strength of earthquakes. This one operates on the laser interferometry principle. Laser beams are bounced back and forth between a set of prisms, with the interference between the beams allowing changes in the beam length caused by an earthquake to be measured. This gives a measure of the strength of the earthquake.
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