Rainbow
A rainbow is an optical phenomenon that typically appears as a colorful arc in the sky, formed when sunlight is refracted through moisture in the air. While often associated with post-rain conditions, rainbows can also occur in mist from waterfalls or ocean waves, and even from garden hoses. The colors of a rainbow consist of seven distinct hues: red, orange, yellow, green, blue, indigo, and violet, appearing in that specific order. This beautiful natural display has inspired countless artistic representations, songs, and cultural legends, often symbolizing themes of love and equality across various societies.
Historically, rainbows have been explained scientifically since the 17th century, with notable contributions from figures like René Descartes and Isaac Newton, who established the nature of light refraction and the spectrum of colors. Rainbows typically require an observer to be positioned between a light source and a water droplet, where the light is refracted and dispersed, leading to the visual effect. Interestingly, a rainbow is not a fixed location but rather a phenomenon that depends on the observer's perspective; it appears as a semi-circular arc, though the complete structure is actually a full circle. Variations such as double rainbows and moonbows further enrich the complexity of these captivating displays.
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Rainbow
A rainbow is an optical phenomenon that can occur when sunlight is refracted through moisture in the air, causing a colorful arc to appear in the sky. Even though rainbows are commonly thought of as forming only after a rain shower, they can sometimes be seen in a waterfall’s mist, in the spray of the ocean's waves, or in a person’s backyard as that individual uses a garden hose. The seven colors that are contained in the sun's white light make up the colors of the rainbow. The seven colors red, orange, yellow, green, blue, indigo, and violet make up the full spectrum of color and usually appear in that order. Rainbows have long been considered one of nature's most beautiful and inspiring sights and have been the subject of many paintings, photographs, songs, and ancient legends. The rainbow has had many symbolic meanings in various cultures, and its symbolism has persisted into the modern era with the rainbow usually connoting love and equality.
Background
The first recorded rainbow in history appeared in the sky after the great flood in the Bible story in Genesis. God sent Noah an ark, which saved Noah, his family, and some animals. For many centuries, scientists have pondered the rainbow’s natural makeup and why it occurs. In 1636, René Descartes realized that rainbows were caused by sunlight being refracted and dispersed by rain. Isaac Newton in 1666 established the feature that rainbows are made up of seven colors, with the truth being that any number can be looked at as arbitrary because the color spectrum contains many shades of similar colors. Evidence of this can be seen by the fact that blue, indigo, and violet are counted as three different colors. It may be that he was comfortable with the idea of the natural order being made up of a series of sevens: seven days, seven notes on the musical scale, and seven known planets at the time.
Thomas Young, a scientist who studied light and its effects, was a propagator of the idea that light behaves as a wave and acts similarly to waves of the sea or waves of sound. His works, as well as those published in the 1820s by George Biddel Airy and in 1908 by Gustav Mie explaining the scattering of light, helped clarify the exact science of the refraction, internal reflection, and dispersion of the sun's light through the atmospheric moisture that results in a rainbow. Most rainbows can be explained using fundamental scientific principles of light and optics, and some are more complicated such as supernumerary rainbows where the light pattern varies from usual rainbows due to light interfering with itself. A double rainbow occurs when the second rainbow is seen outside the primary rainbow with the ordering of the colors exactly opposite those of the inner rainbow with a dark band between the two. The second rainbow is a reflection of the first; hence the sequence of the colors is inverted, as in a mirror. Infrequently, a moonbow, which is the lunar equivalent of the rainbow, can be observed, although it is usually seen as just white because the light of the night sky is too dim to make out individual colors.
Overview
A rainbow is called such because it is usually seen in the form of a bow after rainfall. To see a rainbow one must be situated between the source of the light and the body of water that is reflecting that light. The sun's light is perceived as white light, but, in truth, it contains all the colors of the spectrum. When the light of the sun hits a raindrop, the light changes speed as it attempts to pass through. Since water is denser than light, light slows down as it passes through and speeds up on its way out. Some of the light crosses through to the other side, while some is reflected back toward the direction it came. The reflected light is separated inside the raindrop; this is called dispersion. The light disperses because each color shining on the raindrop has different wavelengths, which means that each color moves at a different speed through matter. As white light goes through air, each color moves at a uniform speed, but when going through a different medium such as water, the colors slow down at various reduced speeds. The speed of the color as it is being reflected off the back of the raindrop will determine the sharpness of the angle that the light bends and its placement in the rainbow. The slower the color is going through the drop, the more it speeds up when leaving, making the angle of the bend sharper. Red light has the longest wavelength; therefore, it is seen at the bottom of the rainbow making the smallest bow.
This can be compared to someone dragging a bench on the floor. The dragged bench moves along at a uniform speed, but if one leg were to be dragged on the floor while the other on rough pavement, the pavement would impede the progress of that leg, causing it to slow down and turning the bench in the process. This is how the color is dispersed inside the raindrop. When the observer is standing at the proper angle and conditions are prime, the observer will see one row of raindrops reflecting one color and the next row reflecting another. The observer will not see more than one color from a single drop, nor a whole rainbow from one row; rather, the entire mist contributes to the rainbow's presence. A rainbow is seen as being in a specific location only in respect to the position of the observer and the source of the light; in fact, it does not exist in a particular place in the sky. A rainbow is really a complete circle, even though it is only seen as a bow because the earth blocks the view of the rest of the spiral. Oftentimes, the entire ring can be seen from an airplane.
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