A rainbow is a meteorological phenomenon that occurs when sunlight is refracted, reflected, and dispersed in water droplets, creating a spectrum of light in the sky. This process typically happens after rain, when the sun shines on the droplets, resulting in a circular arc of colors. The main colors of a rainbow are red, orange, yellow, green, blue, indigo, and violet, often remembered by the acronym ROYGBIV. Rainbows can appear as full circles, but the ground usually obstructs the bottom half, making them look like arcs. They are often seen in the sky opposite the sun and can also occur in mist or spray, such as near waterfalls. Rainbows are not physical objects; they are optical illusions that depend on the observer's position.