Sun glitter is a bright, sparkling light formed when sunlight reflects from water waves. The waves may be caused by natural movement of the water, or by the movement of birds or animals in the water. Even a ripple from a thrown rock will create a momentary glitter.
Light reflects from smooth surfaces by specular reflection. A rippled but locally smooth surface such as water with waves will reflect the sun at different angles at each point on the surface of the waves. As a result, a viewer in the right position will see many small images of the sun, formed by portions of waves that are oriented correctly to reflect the sun's light to the viewer's eyes. The exact pattern seen depends on the viewer's precise location. The color and the length of the glitter depend on the altitude of the Sun. The lower the sun, the longer and more reddish the glitter is. When the sun is really low above the horizon, the glitter breaks because of the waves, which could sometimes obstruct the sun and cast a shadow on the glitter.
Sun glitter can be bright enough to damage one's eyes. Caution should be exercised while observing the glitter.
- C. Cox, W. Munk (1954), "Measurements of the roughness of the sea surface from photographs of the sun's glitter"; Journal of the Optical Society of America, no. 44, pp. 838–850.
- "Sun Glitter". The Weather Notebook. Retrieved Nov 19, 2008.