sateenkaaren

Sateenkaari is an optical and meteorological phenomenon that occurs when sunlight interacts with water droplets suspended in the atmosphere. As light enters a droplet, it is refracted (bent) and dispersed into its component colors. It is then reflected off the inside surface of the droplet and refracted again as it exits. The combined effect of many droplets at specific viewing angles creates a circular arc of colors seen from the observer.

The primary rainbow is the most familiar form. It forms at an angular distance of about 40 to 42 degrees from the antisolar point (the point opposite the Sun). In the primary bow, red appears on the outer edge and violet on the inner edge. A secondary rainbow, produced by light undergoing two internal reflections inside the droplets, appears higher and broader, with colors reversed (red inner edge, violet outer edge) and typically at about 50 to 53 degrees.

In many cases the rainbow is part of a complete circle, although the ground usually obstructs the lower portion. From high vantage points, such as aircraft, a full circle can sometimes be observed. Supernumerary rainbows, faint pastel bands inside the main arc, can occur due to interference effects in small droplets. The phenomenon can co-occur with atmospheric halos or other optical displays when conditions are favorable.

Sateenkaari is not a physical object; it is a perceptual phenomenon dependent on the observer’s position relative to the Sun and rain. In Finnish language and culture, the term describes the colorful arc that symbolizes beauty, hope, and renewal, and it appears in various literary and artistic contexts.