Introduction
A rainbow can be defined as both metrological and optical phenomenon which is seen as a result of the reflection of light in the water droplets more so when it is raining.(David K. & Livingston, W. 67). This phenomenon occurs in the earth’s surface where by a spectrum of light is formed in the sky resulting to a multicolored arc. Usually, rainbows caused by sunlight are seen in the section of the sky which is directly opposite the sky. Whereas in the primary rainbow, the outer part of the arc shows red while the inner part shows violet colors. This type of rainbow is formed as a result of refraction of light as it enters the droplet of water. This light is reflected inside the water droplet and again refracted as it leaves on the other side of the water droplet.
There are several types of rainbows formed in the earth’s atmosphere as per the strength of light as well as the location of the sun at a given time. They can be formed also as a result of two very important processes in science; reflection and refraction. Among others, there exist lunar rainbow, reflection rainbow and double rainbow.( David K. & Livingston, W. 167).
In this research paper, emphasis will be put on the double rainbow, how it is formed and its effect in the environment.
Double rainbow
Double rainbow can be explained as a phenomenon of optics whereby these optics forms a spectrum of light from the shining sun on the droplets of moisture in the atmosphere. It is being argued that technically we experience double rainbow almost most of the time. But we cannot see it since for it to be seen clearly, the sun must be strong and the spectrum rays must be bright.
This explain clearly why cannot see double rainbow at all times but it still remain more of hypothesis which has not been proved. Its proof is at advance stage. (Naylor, J. & David, K 77).
What makes a double rainbow?
As earlier been discussed, a double rainbow refer to two rainbows appearing at once in simple terms. In explaining this, a path of a ray of light is followed to, in and outside the rain droplets. As the law of conservation of momentum puts it, energy neither be created nor destroyed but can be transformed from one form to the other.( David K. & Livingston, W. 57). Therefore, the energy of the light entering the raindrop is not destroyed but part of it remains in the raindrop within the first reflection. We find that the ray is reflected once more and travels to the other side of the raindrop. This results to the production of the primary rainbow that is normally formed with the single reflection of the light. The reflection is always termed as internal since it takes place inside the raindrop.
Another type of double rainbow is the secondary one which is formed as a result of two internal reflections of rays. The difference is, for the secondary rainbow, the double reflection occurs at an angle of 50 degrees rather 42 degrees as for the case of primary rainbow. Here, the blue color which forms one of the rainbow colors emerge at a larger angle of 53 degrees and its effects results to the production of secondary rainbow.( David K. & Livingston, W. 89). The unique feature with this type of rainbow is that it has its colors reversed as opposed to the primary rainbow.
The researchers have it that it is not possible for reflection of light within a raindrop to take place twice and it is also possible to do calculation and find out why the higher rainbows can be seen. But in normal circumstances, these are never seen.
The physical appearance of the double rainbow is that two arcs are seen at the same time with one arc appearing at the top of the other. The arcs are referred to as primary and secondary arcs respectively. Another feature is that it has its colors are reversed as far as the rainbow color orders are concerned. For instance, the red always faces towards the other one in both rainbows. It is only formed when light is reflected twice inside water drop.( David K. & Livingston, W. 90). The secondary rainbow appears fainter than the primary one because of two reasons. The first one being that more lights are lost as compared to the primary rainbow and the second one is that the secondary rainbow is spread on a larger area in the sky. There is the dark area which lies unlit between the primary and a secondary rainbow which is known as Alexander's band after Alexander of Aphrodisias since he first described it.
Double Rainbows Not the Rarest Kind of Rainbows
It is claimed that double rainbows are rare to be seen but even the higher order rainbows as higher as the sixth order can be seen. One of the major factors which affect the visibility of the double rainbow is the light intensity.( Naylor, J. & David, K 98). It is well known that as the light is reflected internally, some of its intensity is lost and this prevent us from seeing the double rainbow. This explanation also clarifies why the primary rainbow is seen to be brighter than the secondary one. In very rare occasions, light might be reflected more than once in raindrop but the background always appear to be too light and this makes an observer not to see the second bow.
How rainbows are formed
Rainbows can be formed or rather can appear to be above or below the horizon as it is explained here. Rainbows can be formed through reflected rays and reflection of rays.( Naylor, J. & David, K 56). When it is formed through reelected rays, then it appears in the water surface below the horizon. The first thing is that the sun is deflected by the raindrops then it is reflected away from the water surface to reach the eye of the observer. The reflected rainbow even if it is the double type always appear partially or even in small puddles.( Raymond L. & Alastair B. 76). Rainbow formed through this method is always visible at most of the time. This is a simple method of light reflection that results to the formation of a rainbow.
The next method in which a rainbow can be formed is through reflection rays. Here, the rainbow is formed by sunlight is reflected off a body of water before reaching any water drop. This happen when the water body is large and the rainbow spread over its entire surface. This type of formation makes the rainbow to appear above the horizon.( Raymond L. & Alastair B. 11). Rainbow formed through this method has its arc higher in the sky and it is not always visible.
Conclusion
All in all, entire rainbow is said not to be located at a given distance from the earth’s surface. It comes from water droplets which are viewed at any given angle with respect to the sun’s rays. Therefore it is very interesting to conclude that a rainbow is not an object and cannot be touched or rather approached physically. For clarity, one should view a droplet of water from a customary angle of 42 degrees opposite the sun. This will give a clear and perfect view of the rainbow and more so, the double rainbow.( Raymond L. & Alastair B. 76).Two observers whereby one sees the other at or under the rainbow will end up seeing two different rainbows at different angles. The colors of the rainbow always appear as per the human vision but the most important thing is that they form a continuous spectrum. Human man eye always sees the rainbow as having the colors of red, orange, yellow, green, blue, indigo and violet. These colors are most highlighted in the sequence of Newton’s sevenfold.( Naylor, J. & David, K 46). One can only think that rainbow is only formed by the water droplets which is not the case. In the real sense, it can be caused by several forms of airborne water. These include mist, spray, and airborne dew.
Work cited
Greenler, R. Rainbows, Halos, and Glories. Cambridge University Press.1980. Print.
Raymond L. & Alastair B.The Rainbow Bridge: Rainbows in Art, Myth and Science. New York: Pennsylvania State University Press and SPIE Press.2001.Print.
David K. & Livingston, W. Color and Light in Nature (2nd ed.). Cambridge University .Press. 2001. Print.
Minnaert, M.& Livingston, W. Light and Color in the Outdoors. Springer-Verlag.1993. Print.
Naylor, J. & David, K. Out of the Blue: A 24-Hour Skywatcher's Guide. Cambridge University Press. 2002. Print.
