Sylvanshine is an optical phenomenon in which dew-covered trees of species whose leaves are wax-covered retroreflects beams of light, as from a vehicle's headlights, sometimes causing trees to appear to be snow-covered at night during the summer. The phenomenon was named and explained in 1994 by Professor Alistair Fraser of Pennsylvania State University, an expert in meteorologicaloptics. According to his explanation, the wax on the leaves causes water to form beads, which become, in effect, lenses.
Reference
Alistair B. Fraser. The Sylvanshine: retroreflection in dew-covered trees. Applied Optics., 33, 21, 4539-4547. 1994
Four things must be present for the sylvanshine to be seen: the proper species of tree, the proper season of the year, dew-covered leaves, and a view looking directly down the beam of light illuminating the tree in an otherwise dark scene.
The sylvanshine is closely related to the heiligenschein.
Fraser, A. B., 1994: The Sylvanshine: retroreflection in dew-covered trees.
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