Interferometryis the analysis of interference patterns which can be used to identifycharacteristics of the original waves, for instance to calculate wavelength.
Theprinciples involve splitting a beam of visible light or another type ofelectromagnetic radiation (i.e UV light) by a beam splitter. Then the recombiningwaves super-impose each other either constructively or destructively to producean interference pattern. Why is interferometry used in science?Interferometry is useful in science as technique becauseit measures small distances to a high level of accuracy by comparing beams oflight.
This is particularly useful in geology and topography, where precisemaps of surfaces can be made. Other uses include astronomy where signals fromtelescopes are combined using interferometers which therefore allow deeper penetrationof light into space.1 Similarly interferometers can also be used in quantummechanics and fibre optics.
Interferometry and preparing for natural disasterOne of interferometry’s biggest new sectors is theanalysis of the earth’s surface. The use of radar interferometry allows scientiststrack changes, from space, to places on earth which are most susceptible tonatural and manmade disasters. Radarinterferometry uses the same basic principles of the Michelson Interferometerbut instead of separating the light waves by the distance travelled, their originalstarting position is altered. This idea is similar to the Young’sInterferometer where the waves travel from a source through two slits toproduce an interference pattern on a screen. In radar interferometry, multipleradar images are created of the wave’s interaction with the ground and then canbe overlapped to give an interference pattern of the surface (Figure 1). Over time these images canbe layered to reveal ground movements and any changes in the interference patternobserved.
The characteristics of these radar images can then be used todetermine particular structures and assess local risk. One such active project,the European initiative Prothego (PROTection of European cultural HEritage fromGe-O-hazards), monitors changes to the geology of the earth’s surface on worldheritage sites and areas of high risk. For instance, the program tracked thesinking of ground above the Jubilee line in Central London after the line was extended(Figure 2). This technology allows a detectionof a few millimeters per year. The technology is allowing govenments who are involvedin the program to identify long term geological issues and to put meausres in place to prevent potentialproblems. References1.