![]() ![]() The sun needs to be less than 42 o above the horizon.You need to be standing with the sun to your back and the rain in front of you.So, the main ingredients to see a rainbow are the following: If the sun is more than 42 o above the horizon, no rainbow will be visible. The higher the sun is in the sky, the smaller the arch of the rainbow above the horizon. At sunset, we would see a full semi-circle of the rainbow with the top of the arch 42 o above the horizon. The lower the sun is to the horizon, the more of the circle we see. We don't see a full circular rainbow however, because the earth gets in the way. ![]() Since the raindrop is circular, the reflection it creates is also circular. This creates the color bands in the rainbow, with blue along the inner portion of the bow, and red on the outside edge of the bow. So, rays that strike the raindrop at this angle of 42 o will tend to form a concentrated, strong beam in which the colors will be widely separated. Since the various colors that make up white light all have slightly different wavelengths, each color becomes slightly separated from the others as the light ray is refracted and reflected. This means that much of the sunlight that is refracted and reflected through the raindrop is focused along this path. The ray drawn here is significant because it represents the ray that has the smallest angle of deviation of all the rays that can enter the raindrop. The angle created at point D is 42 degrees. As it emerges from the raindrop, it is ref racted (bent) again into the direction E. As the light beam enters the surface of the rain drop, it is bent (refracted) a little and instead of continuing to point D, strikes the inside wall of the raindrop at point B, where it is reflected back to point C. This schematic represents the path of one light ray entering a raindrop at point A. As light enters the raindrop, it is refracted (the path of the light is bent to a different angle), and some of the light is reflected by the internal, curved, mirror-like surface of the raindrop, and finally is refracted back out the raindrop toward the observer. To understand how the bow is formed, we need to consider the path of a ray of sunlight through a single round raindrop. Typically, we only see a portion of the entire circle, leading to the bow shape. The "bow" part of the word refers to the fact that the rainbow is a group of nearly circular arcs of color all having a common center. The traditional rainbow is sunlight spread out into its spectru m of colors and diverted to the eye of the observer by water droplets. The rainbow is one of the more spectacular light shows observed on earth. HOW DO RAINBOWS FORM? "A rainbow in the east will be followed by a fine morrow, in the west by a wet day." - Weather Proverb What is a rainbow? ![]()
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