arcobaleno

An arcobaleno, in English a rainbow, is a meteorological and optical phenomenon that appears as a multicolored arc across the sky. It is created by the refraction, dispersion, and reflection of sunlight within raindrops. The light entering a drop is refracted and split into its component colors; after reflecting from the inner surface of the drop, the light is refracted again as it exits, forming a spectrum from red on the outer edge to violet on the inner edge. Most observers see a primary rainbow, and a fainter secondary rainbow may appear outside it, caused by two internal reflections. A rainbow typically occurs when sunlight shines from behind the observer onto rain in front of them, with the sun at a low angle relative to the horizon.

The primary and secondary rainbows differ in order and brightness; the secondary rainbow has its colors reversed and is fainter due to the extra reflection. In some conditions, interference among light waves can produce faint supernumerary bows just inside the main arc.

Rainbow arcs can form into full circles under suitable conditions, particularly from high vantage points or at night with mist and a strong light source such as the sun or moonlight, though the horizon often truncates the circle.

In Italian, arcobaleno combines arco (arch, bow) and baleno (flash or gleam); in English the term is simply rainbow. It is widely used as a symbol of beauty, hope, and diversity and is associated with LGBT pride through the rainbow flag and related iconography. Across cultures, rainbows have been interpreted in various ways, from omens to bridges or covenants.