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A freshwater lens on an island. In hydrology, a lens, also called freshwater lens or Ghyben-Herzberg lens, is a convex-shaped layer of fresh groundwater that floats above the denser saltwater and is usually found on small coral or limestone islands and atolls.
The first physical formulations of saltwater intrusion were made by Willem Badon-Ghijben in 1888 and 1889 as well as Alexander Herzberg in 1901, thus called the Ghyben–Herzberg relation. [15] They derived analytical solutions to approximate the intrusion behavior, which are based on a number of assumptions that do not hold in all field cases.
When a Ghyben-Herzberg lens is fully formed, its floating nature will push a freshwater head above mean sea level, and if the island is wide enough, the depth of the lens below mean sea level will be 40 times the height of the water table above sea level. On Diego Garcia, this equates to a maximum depth of 20 m.
Lens (hydrology) From a page move : This is a redirect from a page that has been moved (renamed). This page was kept as a redirect to avoid breaking links, both internal and external, that may have been made to the old page name.
This is an accepted version of this page This is the latest accepted revision, reviewed on 1 February 2025. Water located beneath the ground surface An illustration showing groundwater in aquifers (in blue) (1, 5 and 6) below the water table (4), and three different wells (7, 8 and 9) dug to reach it. Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in ...
An axicon is a specialized type of lens that has a conical surface. An axicon transforms a laser beam into a ring shaped distribution. [1] They can be convex or concave and be made of any optical material. The combination with other axicons or lenses allows a wide variety of beam patterns to be generated.
Gerhard Heinrich Friedrich Otto Julius Herzberg, PC CC FRSC FRS [1] (German: [ˈɡeːɐ̯.haʁt ˈhɛʁt͡sˌbɛʁk] ⓘ; December 25, 1904 – March 3, 1999) was a German-Canadian pioneering physicist and physical chemist, who won the Nobel Prize for Chemistry in 1971, "for his contributions to the knowledge of electronic structure and geometry of molecules, particularly free radicals". [2]
The lens focuses light in the same way as a conventional lens. Gradient-index (GRIN) optics is the branch of optics covering optical effects produced by a gradient of the refractive index of a material. Such gradual variation can be used to produce lenses with flat surfaces, or lenses that do not have the aberrations typical of traditional ...