RiverPhysix: exploring light on water
Distant reflected lights and dark foreground water can coexist because
source–observer geometry, angle-dependent reflection, and surface
slopes determine which light reaches the eye. Fresnel reflectance
alone does not predict a sharp boundary.
For a smooth, lossless air–water interface with illustrative indices
1.00 and 1.33, normal-incidence reflectance is 2.00593122%. At
Brewster’s angle, 53.0612373°, only the p component vanishes;
unpolarized reflectance is 3.85562852%, not a minimum. Equal incidence
and reflection angles are measured from the surface normal.
For an observer at height h and a source at height H and horizontal
separation L, the compatible reflection point is d = hL/(h+H).
Roughness illustrations are not measurements or a calibrated model of
a particular river.
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