regnboga

Regnboga is a meteorological optical phenomenon in which a multicolored arc appears in the sky, opposite the sun, formed when sunlight is dispersed by water droplets in the atmosphere. The arc typically displays a sequence of colors, with red on the outer edge and violet on the inner edge.

The physical process involves refraction, dispersion, and reflection of light within raindrops. As sunlight enters a droplet, it slows and bends, separating into its component colors. The light reflects off the inside of the droplet and exits, refracting again on the way out. The geometry causes rays to emerge at a characteristic angle from the direction opposite the sun, producing the primary rainbow at about 40 to 42 degrees. A secondary rainbow results from two internal reflections and appears at roughly 50 to 53 degrees, with the color order reversed.

Observational notes include that rainbows are seen when there are many small droplets in the air and the sun is relatively low. The arc is usually a semicircle or segment of a circle, but under suitable conditions a full circle can be visible from an elevated viewpoint or from within a mist or cloud.

Variants and related phenomena include double rainbows, where a fainter outer arc surrounds the brighter inner one, and supernumerary rainbows, which are faint pastel bands caused by interference of light waves in small droplets. Fog bows are similar but fainter and with less distinct coloring due to very fine droplets.