Rainbows & Blue Sky

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Rainbows & Blue Sky

Introduction

The formation of the rainbow and the blue appearance of the sky are both concepts that emulate the visibility of light. This is because both natural aspects appear as they do due to the concept of dispersal and the bending of light. The rainbow in particular appears when there is double refraction of light with a suspended droplet of water acting as the prism, whereas, the blue appearance of the sky is due to the dispersal of the white sunrays into different colors with the blue light holding the most intensity. This research paper will therefore look at how the two natural aspects explain the visibility of light and the availability of the different colors in the dispersal process of a single ray of light.

Discussion

The formation of the Rainbow

A rainbow demonstrates the dispersion of light. It shows that a single ray of light is composed of several other wavelengths and each wavelength can be associated with a particular color. A rainbow is commonly seen when an individual’s back faces the sun as the head is tilted about 40 degrees into a place in the atmosphere where the rays of the sun meet suspended droplets of water. The droplets of water act as dispersing prisms and these prisms break refract the sunrays to create an appearance of specific colored wavelengths to the human eyes. Analyzing the formation of the rainbow will create understanding on concepts such as refraction and dispersion of light while finding reasons behind the arrangement of colors as they appear

In the concept of refraction, the droplets are the responsible parties. The speed of the ray first determines the bending of the light due to the decrease in speed as it hits the droplets. After the ray of light has bent to the normal, water as the medium with the higher density forces the ray to bend away from the normal increasing the speed enough for the ray to bounce back. In this instance, it is said that refraction of light has occurred.

This happens to every single ray and to all the paths that each individual ray takes. To explain how an individual on the ground surface sees the ray is that the light initially bends to the normal and inside it is refracted back. This makes the ray to hit the droplets at another angle causing an internal refraction that when it leaves the droplet and the light is dispersed the viewer sees the dispersed wavelengths in the form of colors. Of course, there are rays that exit the prisms without any particular angle and these are therefore unobservable to the viewer.

Diagrams showing the refraction and the dispersal of Light rays from the sun to the viewer, Source:

The different colors seen also appear as they do due to certain reasons. The common colors from top to bottom are Red, Orange, Yellow, Green, Blue, Indigo, and Violet (ROYGBIV). This means that the largest wavelength consists of the red color, while the shortest one the violet or sometimes the Blue. The boundaries of dispersal not being parallel to each other due to double refraction, is the reason behind the different colors and the blue one is usually of more intensity than of the red due to the shorter wavelengths. The common angle of deviation to the viewer’s eyes for the red color is usually 42 degrees but the blue is at 40 degrees explaining that steepness is the reason behind the high intensity. Upon understanding the concept of refraction, deviation, and dispersal of light, this is how the rainbow is formed.

The rainbow often takes an arc-like shape across the sky. An observer will see this arc with the red color on the outermost part followed by the rest and ending with the violet as the innermost curve. The half circle appearance is often an illusion because the rainbow in the real sense forms a complete circle. The formed curves are able to form from the atmosphere all the way down because there are droplets that maintain the process at the specific degree of deviation with each droplet receiving the light and refracting to the observer’s eyes.

When it comes to viewing the rainbow, the steeper the angle of the viewer, the more the red light, or color becomes visible than the blue and vice versa. This theory therefore explains the reason for observing the red light as the top most one and the blue as the bottom and innermost curve. Rainbows have been known to appear in many other areas with the presence of water and sunrays and not only in the atmosphere because the refraction relationship of the ray of light and the droplet of water is the main ingredient for its formation. This is common in waterfalls and a water sprinkler among others. Suspended droplets of water, a ray of light and a refraction process are therefore the three necessities of the formation of a rainbow.

Diagram showing an observer viewing the rainbow and the formation of the different colors of the arc, Source:

Reasons for the Blue Sky

Commonly, a clear and cloudless day makes the sky appear blue in color. This is because, scientifically, the molecules that are contained in the atmosphere tend to scatter the blue rays from the refracted sunrays further than the red rays. Other times such as sunrises and sunset, a reddish or orange appearance covers the sky because at this time, the blue light has been scattered from the sun and away from sight. This concept is similar to that of the formation of the rainbow, only that the air molecules among others that are present in the atmosphere are responsible for the creation of the prisms that break down the white color from the sun into other individual colors. Isaac Newton is among the great scholars that supported this theory and used a prism to illustrate the dispersal of light that breaks down to form various colors.

Diagram showing the dispersal of white light to dorm, a spectrum of colors, Source:

Like the wavelength concept used in the explanation of the difference in intensity in the blue color of the rainbow arc over the red color, the same aspect appliers to this scenario. This is such that, the blue color has a shorter wavelength and more concentration whereas the red color has a longer wavelength and lesser concentration. The other colors within the spectrum also affect the appearance of these colors such that they have individual aspects with the orange and yellow colors siding with the red and the green and violet, the blue. The human retina however has a higher tendency to identify the Red, Blue, and Green colors, therefore giving the ability of the color vision.

Other explanations that attempted to explain this phenomenon include the Tyndall Effect. This is because he discovered that the passing of light through a fluid with suspended particles resulted in the dispersion of light. His research also proved that the shorter wavelengths that comprised of the blue color was scattered more strongly than the red. The demonstration was similar to that of the passage of a ray of light through the atmosphere where he used a tank of water with milk and soap in it. From one side the beam appeared to be blue in color but from the other, it came out reddened.

The Tyndall effect was studied at a deeper level by a physicist called Rayleigh and the concept became the Rayleigh scattering. Unfortunately, not many agreed to Tyndall and Rayleigh’s perception that the blue color of the sky was due to the dust particles and droplets from water vapor in the atmosphere. Einstein therefore created a better explanation using the electromagnetic field concept that light waves induced the reaction of the molecules that facilitated the dispersal of light.

Conclusion

Overall, it is safe to say that there are certain aspects that make both processes different despite their common reliance on the dispersal and visibility of light. The formation of the rainbow is attributed to the refraction by suspended water particles. On the other hand, the dispersal of the white light in the atmosphere to result in the blue color is due to the atmospheric molecules. In both cases however, the difference in the color wavelengths has significant effect on the appearance of the natural phenomenon. These two concepts are great evidences of the visibility of light and the effects of the dispersal and bending processes of the same.