The document discusses how rainbows are formed. Rainbows are an optical phenomenon that occurs naturally in the Earth's atmosphere when sunlight interacts with water droplets, typically in the sky after it rains. The colors of the rainbow - red, orange, yellow, green, blue, indigo, and violet - correspond to the different wavelengths of light. Red appears outermost in the rainbow because it has the longest wavelength. A rainbow forms when sunlight enters and reflects off the inside surfaces of raindrops, undergoing one internal reflection and refracting at two surfaces before leaving the raindrop and reaching the observer's eye.