In a process called dispersion, longer wavelengths those we see as red bend less than shorter blue ones [source: Mass ]. That's why red is at the top of the rainbow in that longer, lazier arch, and blue is at the bottom in a shorter, tighter one.
A double rainbow occurs when the light is reflected twice in the drop. It means you can see two different reflections, coming from different angles [source: Plait ]. This leads to something that is actually really cool — instead of seeing red at the top and blue at the bottom like a regular ho-hum rainbow, the secondary rainbow which is higher and lighter in color than the primary has the colors reversed [source: Margusity and Andrews ]. Yup, Vib G. Yor — doesn't have the same ring as Roy G.
Biv, does it now? A much rarer phenomenon is called a "twinned" rainbow. That's when two separate arcs break off from the same primary base. Researchers from Disney yup, that Disney were trying to find a way to simulate and animate rainbows better, and stumbled upon the idea that raindrops of different shapes or sizes usually from two rain showers combining lead to twinned rainbows [source: ScienceDaily ]. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close.
Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Forces of Nature. Raindrops act as prisms, bending and reflecting the sunlight that falls on them, just like a crystal hung in a sunny window. As light enters water, the path it takes changes. How much the direction changes is a function of the color of the light. You probably noticed that a smooth water surface can act like a mirror and reflect light. If the light beam entering the raindrop reaches the back of the drop at a certain angle, it undergoes a reflection and heads back toward the sun.
As the light exits the raindrop and re-enters the air, its path bends an amount that again depends on the color. This bending of the light as it enters and leaves the drop disperses the light of the sun into its spectrum of colors that form the rainbow. Sometimes the light reflects twice off the back of the raindrop; this leads to the secondary rainbow.
The second reflection causes the order of the colors in the bow to reverse. A rainbow occurs when white sunlight scatters off of raindrops in the air. Because of the dispersive properties of water, the different colors of light in the sunlight bend refract different amounts when entering and leaving the raindrop. As a result, the different colors leave the raindrop at different angles, making you see the different colors at different locations in the sky.
Because this scattering is a geometric effect that depends on the direction of the original incoming sunlight, the rainbow forms as a circle or part of a circle that is centered on the point exactly opposite of the sun. The main rainbow called the "primary rainbow" involves sunlight entering the raindrop, reflecting once off the inner back surface of the raindrop, and then exiting the raindrop.
Additionally, light can bounce twice off the inner surface of the raindrop before exiting. The second reflection causes these light rays to exit at an angle that is very different from that of the light rays that only reflect once. Therefore, a secondary rainbow forms that has a larger radius than the primary rainbow.
The secondary rainbow is created by the same sunlight and the same refraction process as the primary rainbow, so it is also centered on the point exactly opposite the sun.
Because of the additional reflection, the colors in the secondary rainbow are reversed in order compared to the primary rainbow. Since some light is lost out of the raindrop with every reflection, the secondary rainbow is much fainter than the primary rainbow. In principle, the secondary rainbow is always present.
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