Sylvanshine is an optical phenomenon in which dew-covered trees of species whose leaves are wax-covered retroreflect 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 meteorological optics. According to his explanation, the wax on the leaves causes water to form beads, which become, in effect, lenses. These lenses focus the light to a spot on the surface of the leaf, and the image of this spot is directed as rays in the opposite direction.