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Under ideal conditions, an observer looking up at the water surface from underneath sees a perfectly circular image of the entire above-water hemisphere—from horizon to horizon. Due to
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Underwater photographers sometimes compose photographs from below such that their subjects fall inside Snell's window, which backlights and focuses attention on the subjects.
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at the air/water boundary, Snell's window compresses a 180° angle of view above water to a 97° angle of view below water, similar to the effect of a
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The edge of Snell's window, in this case the boundary between reflected bottom (teal) and refracted sky and above-water structures (blue and gray)
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sees everything above the surface through a cone of light of width of about 96 degrees. This phenomenon is caused by
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in the water will veil the image behind a cloud of scattered light.
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A diver viewed from below who appears inside of Snell's window.
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238:Explanation of the physics behind Snell's window
156:David K. Lynch and William Livingstone (2001).
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243:Under-water photograph showing Snell's window
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46:of light entering water, and is governed by
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222:circle-of-light water critical-angle 180.
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183:Martin Edge and Ian Turner (1999).
268:. You can help Knowledge (XXG) by
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216:. The Macmillan Company. p.
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210:Robert Williams Wood (1914).
186:The Underwater Photographer
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159:Color and Light in Nature
52:total internal reflection
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124:Dave Hughes (1990).
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