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A diver viewed from below who appears inside of Snell's window. Snell's window (also called Snell's circle [1] or optical man-hole [2]) is a phenomenon by which an underwater viewer sees everything above the surface through a cone of light of width of about 96 degrees. [3] This phenomenon is caused by refraction of light entering water, and is ...
English: Snell's window as seen through an underwater tunnel at the St. Louis Zoo. Caustics in the water are visible near the sun. The black line through the frame is a gasket between segments of the tunnel.
Snell's law (also known as the Snell–Descartes law, the ibn-Sahl law, [1] and the law of refraction) is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass, or air.
Through "Snell's window" (top), we see some of the scene above the water, including the handles of the ladder (right of center). The color-fringing of the light (top) and of the edge of Snell's window is due to variation of the refractive index, hence the critical angle, with wavelength. Reason I can't comment on its merits as a sports photo.
Willebrord Snellius [1] [2] (born Willebrord Snel van Royen) [3] (13 June 1580 [4] – 30 October 1626) was a Dutch astronomer and mathematician, commonly known as Snell. His name is usually associated with the law of refraction of light known as Snell's law. [5] The lunar crater Snellius is named after Willebrord Snellius.
For equal permeabilities (e.g., non-magnetic media), if θ i and θ t are complementary, we can substitute sin θ t for cos θ i, and sin θ i for cos θ t, so that the numerator in equation becomes n 2 sin θ t − n 1 sin θ i, which is zero (by Snell's law).
A Brewster window. Gas lasers using an external cavity (reflection by one or both mirrors outside the gain medium) generally seal the tube using windows tilted at Brewster's angle. This prevents light in the intended polarization from being lost through reflection (and reducing the round-trip gain of the laser) which is critical in lasers ...
Martin Edge (op cit, p223) observes "I was once under the impression that the deeper you went the more [of snell's window] could be included [in the photograph]. This is incorrect! To photograph the full circle you need a fisheye lens equivalent to a 12mm lens on a 35mm format."