A rainbow is a meteorological optical phenomenon that occurs when sunlight is refracted, reflected, and dispersed by water droplets in the atmosphere. It appears as a circular arc of colors in the sky, with red on the outer edge and violet on the inner edge, transitioning through the colors of the visible spectrum: red, orange, yellow, green, blue, indigo, and violet.
The formation of a rainbow involves two primary processes: refraction and reflection. When sunlight passes through water droplets suspended in the air, it undergoes refraction, which causes the light to change direction as it enters and exits the droplet. This bending of light is accompanied by dispersion, where different colors within the white light spectrum are separated due to their varying wavelengths. Upon exiting the droplet, the refracted light is then internally reflected off the inner surface of the droplet before exiting into the surrounding atmosphere.
The result is the familiar arc of colors that we perceive as a rainbow. The colors are arranged in a specific order due to the varying angles at which the light is refracted and reflected within the droplets. The innermost color, violet, is refracted at a steeper angle than the outermost color, red, resulting in the distinct color sequence.
Rainbows are often observed in the sky opposite the sun, typically when rain is falling and the sun is shining from behind the observer. Double rainbows can also occur, where a fainter and broader secondary arc appears outside the primary rainbow due to an additional reflection within the water droplets.
The beauty of a rainbow lies in its vibrant and harmonious display of colors, created by the interaction of sunlight and water droplets in the atmosphere. It has fascinated humans for centuries and is often associated with positive symbolism and wonder.