Rainbows, Spectrum of Colors - Report Example

Rainbows Rainbows A rainbow is a fascinating natural phenomenon that are attractive to look at. A wide range of definitions ofthe rainbow has been documented most of which are associated with myths and traditions all over the world. Layman explanations such as The rainbow is made up of seven colors have been seen in a wide range of materials. Such explanations provide obvious observable facts without giving proper background foundational principles regarding the origin of Rainbows. However, scientific explanations offer more substantial and tangible explanations that have been confirmed in wide experiments that have been performed in the laboratory environment. These explanations have led scientists to develop different careers. For example, sorting algorithms useful in demonstrations of principles behind rainbow sort (Dominic, 2004). In addition, the observations are very useful to researchers interested with this impressive natural occurrence. In science various outstanding explanations exist about the rainbow. For example, a rainbow is an arc of concentric seven colored bands that develops when light from the sun interacts with raindrops. The light is refracted as it enters the raindrop causing different wavelengths of visible light to separate. Similarly, Bailey explains that the formation of the rainbow can be understood in the context of ray optics as resulting from light that is reflected internally once inside a liquid droplet (Bailey, 2004). All these explanations are tied together in the basic principles of refraction and reflection of light. Under these broad categories of properties of light, proper understanding of composition of white light and how dispersion of light occurs is critical in understanding the principles behind the rainbow. White light is composed of seven colors namely Red, Orange, Yellow, Green, Blue, Indigo and Violet in order of the wavelength. Dispersion of white light is the process through which light is dissociated into its constituent seven colors (Duncan & Heather, 2001). Light enters the rain droplets and undergoes refraction. In the process, the seven colors of visible light are dissociated according to their wavelength. Red light with a longer wavelength is bent least compared to violet light with a shorter wavelength which is bent more. The red light appears at the top of the spectrum because it is deviated least while the violet light appears at the bottom of the spectrum because it is deviated most. The other colors overlap within the spectrum but are conspicuous to the human eyes. As a result, a spectrum of colors is produced explaining precisely how the rainbow is formed. Special optical devices such as the glass prisms can be used to understand the whole concept of rainbows as shown in Figure 1. In the figure, white light enters the prism as shown in the diagram undergoes basic refraction and produces a spectrum of colors as shown. This spectrum is produced because of the fundamental concept that different colors in the white light respond differently to the glass material of the prism (Cutnell & Johnson, 2004). Understanding the basic concepts of light are critical in understanding a rainbow. Rain is made up of droplets that behave like prisms. The red and the blue beam enclosing the spectrum can be represented as illustrated on Illustration 2. In this case white light is first dissolved into its constituent colors for simplicity red and blue are used. The beams undergo a reflection at the boundary of the droplet and are further refracted as they emerge out of the droplet. The rays advance to the human eye which detects the spectrum that is seen as a rainbow (Cutnell & Johnson, 2004). It is however important to notice that the direction from which the observation is made is necessary. The reason behind the refraction of light is primarily due to the change of refractive index. In this case, the refractive index of air is different from that of water, and it reflects the different velocities with which light travels in these media. In addition, the angles at which the beams emerge from the droplet is different or else the colors will not be visible (Cutnell & Johnson, 2004). The red light emerges at an angle of 42° whereas blue light emerges at an angle of 40.6° relative to the incident rays from the sun (Dominic, 2004). A rainbow is often seen as a circular arc or bow of seven colors in the sky. An observer on the earth observes a half cycle with red color more conspicuous at the top of the bow. Observations made from the sky indicate the rainbow is usually a full circle. This is because observers on the ground are prevented by the ground from seeing the whole circle but when in the airplane, one can quickly look up and down and see suspended droplets that disperse the white light from the sun to reveal a complete circular rainbow. The circle or semicircle results from a collection of a large number of suspended droplets in the atmosphere which have the ability disperse white light and to concentrate the light dispersed at angles of deviation between 40° to 42° to relative to the incident path of white light, and reflect the it to the observer. However, the reason red light is seen more clearly than the other colors need to be known. The red beam is reflected out the droplets at steeper angles compared to the beams of other colors. When an observer observes at an angle that is steeper than the rest of the beams, droplets from the line reflect red light at a trajectory directed into the observer’s eyes giving red light at very steep angle. The blue beam is dispersed at a lesser angle along a specified trajectory which passes above the observers head. This means that the red color overlaps other colors in the spectrum because of high deviation and, as a result, appears more conspicuously compared to the other colors in the same spectrum. In conclusion, therefore, each raindrop emits a spectrum of colors. In the rainbow we observe the reflected light contributed from many droplets (Dominic, 2004). The rain drops lower in the sky provide the observed blue color whereas those above the sky give the red color as indicated in illustration 3. The anti-solar point can explain how the bow is formed. Looking at the ground during a sunny day, shadows are seen 180° away from the sun creating what we call anti-solar points. These points are usually below the object when the sun is directly above and above the horizon if the sun just sets. Figure 4 explains this observation (Cutnell & Johnson, 2004). These anti-solar points tell us where the rainbow is likely to be developed since the colors dispersed from the droplets emerge at angles that can be measured with respect to the anti-solar points. In layman language, any rainbow we observe in the sky is due to pigments dispersed from the raindrops at 40.6° to 42° measured relative to the direction of the anti-solar direction. In addition, every raindrop 42° of the anti-solar line reflects red light into our eyes and looking at every drop reflecting red color at this angle we would actually observe a circle unfortunately, the horizon interferes and the only thing seen is an arc as shown in illustration 4. Therefore, full rainbows are seen from the top of a mountain or an airplane. Finally, as noted in illustration 6, Raindrops that positively contribute to the arc all lie on a cone with its apex in the observer’s eyes which shows dispersed light from a collection of many droplets. References Bailey, J. (January 01, 2007). Rainbows, Polarization, and the Search for Habitable Planets. Astrobiology, 7, 2, 320-332. Cutnell, J. D., & Johnson, K. W. (1995). Physics. New York: J. Wiley. Dominic S. (2004). Rainbow Sort: Sorting at the Speed of Light. Department of computer science, University of Auckland. Duncan K. and Heather K. (2001). GCSE Physics, 4 Ed. Book print S.L., Barcelona, Spain [5[-of-white-light? Read More