Good Research Paper About The Rainbow Formation – Explained Through Physics
One of the natural phenomena that I wondered about was the formation of rainbows. Almost every time rain ends or there is a mist of vapor in the streets, I tend to see rainbows. So I asked myself, how do rainbows form, why is that rainbows are always semicircular in shape, and why are they always arranged in the order: red, orange, yellow, green, blue, indigo, and violet?
My limited knowledge in physics came in handy to answer these questions. Accordingly, for the first question, white light just like the light that comes from the sun is actually made up of different colored lights. These different lights (component lights) have different wavelengths and frequencies – two properties of waves. I learned in physics that prism could separate these lights so that they become distinct from one another. What a prism does is that it disperses the white light into red, orange, yellow, green, blue, indigo, and violet (ROYGBIV).
The Dispersion takes place in three steps. As the light enters the prism, the light undergoes refraction. The light then travels within the prism at different speed (much slower than it did when it was travelling in air). After refracting, the light inside the prism undergoes internal reflection, which further disperses the light components. After reflection, another refraction process happens as the components lights exit the prism into the air. The net effect is that the component lights are moved away or dispersed from one another creating the rainbow (Durte and Piper 303). I learned through research that a droplet of water can act as prism. So the water droplet actually creates the rainbow (The Physics Classroom).
As for why do I always see a semicircular rainbow, I have learned that we can only see by reflected light. In other words, light has to enter our eyes so we can see it. I learned that in order for us to observe a rainbow, there must be a certain angle between us and the sun and the water droplet (University of Illinois). That angle is 420, with us in the middle. The earth is a sphere; hence water droplets should always be at that angle as they move away from us in order for us to see the light that they reflect. The earth is a sphere, hence the location of the droplets that could reflect light to us at a consistent 420 are arranged in a semi-circular location. The shape of the rainbow is actually the location of the droplets that are 420 away from the line between us and the sun (The Physics Classroom).
Lastly, as to why the light components are always arranged in ROYGBIV, the answer is related to the angle of refraction. Accordingly, during the refraction process (refraction during the exit of the light from the prism or water droplet) the red light is always refracted at the steepest angle and the violet light is the list steep. The order of the degree of steepness of the each light component follows the ROYGBIV. This is the reason why “red” is always at the top of the rainbow and violet is always at the bottom. It should be noted, however, that if a prism is used, the arrangement of the colors can be reversed depending on the orientation of the prism. But for rainbows created by water droplets, the order is always the same (Palma).
Understanding how natural a phenomenon happens through physics is enjoyable. It, however removes the mystery on how the phenomenon happen – mystery is usually the reason why we appreciate a phenomena. Nevertheless, for me rainbows remain enjoyable and beautiful to see, despite the fact that I know how they are formed. Learning physics and appreciating nature go hand and hand, therefore. We will only be able to understand the true beauty of nature once we understand even just the basic principles in physics.
Durte, F.J. and Piper, J.A. Dispersion theory of multiple-prism beam expanders for pulsed dye lasers. Optics Communication. 43.5(1982): 303 – 307.
Palma, Christopher. The Wave Properties of Light. 2014. Department of Astronomy and Astrophysics, The Pennsylvania State University. 15 January 2015. <https://www.e-education.psu.edu/astro801/content/l3_p2.html>.
The Physics Classroom. Rainbow Formation. 2014. Web. 15 January 2015. <http://www.physicsclassroom.com/class/refrn/Lesson-4/Rainbow-Formation>.