What causes rainbows?

Rainbows are formed through the interaction of sunlight and water droplets in the atmosphere. When sunlight enters a raindrop, it slows down and bends—a process called refraction—because light travels at different speeds in air and water. Inside the droplet, the light reflects off the inner surface, then refracts again as it exits the droplet back into the air. This bending and reflecting cause the light to spread out into its component colors, creating a spectrum. The colors you see in a rainbow—red, orange, yellow, green, blue, indigo, and violet—are the result of this dispersion of light. Each color bends by a slightly different amount, with red bending the least and violet the most. For a rainbow to be visible, the observer must be positioned with the sun behind them and rain or mist in front. The specific angle at which the light exits the raindrop, usually around 42 degrees relative to the incoming sunlight, determines the circular arc of the rainbow you see. In summary, rainbows are caused by the refraction, reflection, and dispersion of sunlight in water droplets, which separates the light into its different colors and forms the beautiful arcs we observe in the sky after rain.

Rainbows are formed through the interaction of sunlight with water droplets in the atmosphere. When sunlight enters a raindrop, it slows down and bends—a process called refraction—because light travels at different speeds in air and water. Inside the droplet, the light reflects off the inner surface and then refracts again as it exits the droplet back into the air. This bending and reflecting of light cause the sunlight to spread out into its component colors, creating a spectrum—from red on the outer edge to violet on the inner edge. This separation of colors is called dispersion. Because each color bends by a slightly different amount, the light exits the droplets at different angles, allowing an observer to see the distinct bands of colors that form a circular arc in the sky. For a rainbow to be visible, the observer must be positioned with the sun behind them and rain or mist in front. The typical angle for viewing a primary rainbow is about 42 degrees from the direction opposite the sun. Sometimes, a secondary rainbow appears outside the primary one, caused by light reflecting twice inside the raindrops, which results in reversed colors and a dimmer appearance.