![]() ![]() But the process of working with Indigo also intimidated me. ![]() I’ve always been fascinated with the color of indigo, as I’m sure many would agree with me. One of the best classes I signed up for last summer was a fresh leaf indigo dyeing with Graham Keegan at the Marshfield School of Weaving. The higher the sun is in the sky, the less of a rainbow is visible above the horizon.We are almost out of winter and I’m still trying to catch up with all my travels from last summer. Right at sunset, we would see a full semicircle of a rainbow with the top of the arch 42 degrees above the horizon. The closer the sun is to the horizon, the more of the circle we see. We don't actually see the full circle because the earth gets in the way. Thus, a rainbow is actually a circle centered on the point directly opposite the sun from the observer-the so-called antisolar point-with an angular radius of 42 degrees. Because of this symmetry, so long as the raindrop is viewed along a line of sight that makes a 40- to 42-degree angle with the direction of the sun, the various colors of light will be visible. This is why we see rainbows as a continuous band of colors with red on top and violet on the bottom.Ī typical raindrop is also spherical and therefore its effect on sunlight is symmetrical about an imagined axis connecting the center of the drop and the sun. The other colored light frequencies are bent at angles in between these two. Shorter violet light waves are only bent at an angle of 40 degrees. When sunlight hits a raindrop, the red light waves are bent at an angle of 42 degrees from their original direction from the sun. Longer wavelengths are bent at larger angles, so longer wavelengths are bent less than shorter wavelengths. ![]() For example, a prism can also create rainbows because the glass, like the raindrop, bends the different colors of light at slightly different angles. As a result, white light can be broken up into its component colors by being passed through certain medium. Each color has a different wavelength, or frequency, which refracts slightly differently when it passes from one medium to another. ![]() When light hits the rain at just the right angle, it is refracted through a raindrop and into our eyes, causing us to see a rainbow.īut how does the "white" sunlight produce a multicolored rainbow? Sunlight, or "white" light, is actually made up of continuous bands of different colored light-red, orange, yellow, green, blue, indigo and violet. The light then turns again as it moves out of the raindrop and back into the air at its original speed. In the case of a rainbow, when sunlight hits a raindrop it does not move as fast through the water as it does through the atmosphere, so it bends a little. This is because the wheels moving on the pavement are able to roll faster than the wheels on the grass. This is analagous to pushing a shopping cart at the edge of a parking lot: if the wheels on one side roll off the pavement onto an adjacent area of grass, the cart will start to turn toward the grass. Sunlight passing through raindrops causes rainbows via a process called refraction, which is the bending of light as it passes from one medium to another. Jeff Waldstreicher, a meteorologist with NOAA's National Weather Service, provides this answer. ![]()
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