what causes a rainbow

A rainbow is caused by the refraction, dispersion, and reflection of sunlight as it passes through raindrops. When sunlight enters a raindrop, the light bends (refraction) and spreads out into its various colors (dispersion) because each color bends at a slightly different angle due to different wavelengths. The light is then internally reflected inside the raindrop and refracted again as it exits, sending the spectrum of colors to the observer’s eye. This process creates the visible arc of a rainbow, usually seen when the sun is behind the observer and there are water droplets in front of them. Sunlight is composed of many colors, and a rainbow shows these as red, orange, yellow, green, blue, indigo, and violet in a concentric arc. A rainbow is actually a full circle, but from the ground, we typically see only the upper arc because the Earth blocks the rest. The angle of light deviation inside the drops is about 42°, which is why a rainbow forms at that specific angle relative to the observer’s line of sight opposite the sun.