“My heart leaps up when I behold A Rainbow in the Sky,” is how the English poet, William Wordsworth, described the effect of watching a rainbow on his mood in his poem My Heart Leaps Up. A rainbow displays seven colors—red, orange, yellow, green, blue, indigo, and violet—which are always displayed in this same order. We owe the idea that rainbows consist of seven colors to Isaac Newton; before that, many people believed rainbows showed only five colors and in Baltic countries, it was believed that a rainbow showed only two colors: red and blue. Before the 17th century, people did not understand the rainbow phenomenon; it was not until Rene Descartes recognized that light coming from the Sun passes through rain droplets and splits into various colors.
Actually, there is no definite number of colors in a rainbow; every color mixes with other colors, as there are no boundaries between a color and another, making it impossible to differentiate. Besides, a rainbow does not physically exist; it is just a “distorted” reflection of the Sun’s light as it passes through raindrops, creating this amazing phenomenon. Normal wavelengths are, in short, bent to create a rainbow of colors that each culture bases its own perception of. When Newton made up his mind that a rainbow contains seven colors, it was after a long history of considering the number seven important in the universe: seven musical notes, seven days of the weeks, and before the discovery of Neptune, seven planets.
Rainbows are quite common; however, you do not have to wait for a rainbow to occur spontaneously in order to see it. You can easily create your own. Creating a rainbow requires a shallow pan, water, a flashlight, a piece of paper, and a mirror. The point is to refract light the same way it is refracted from the Sun by creating the same conditions. First, you have to fill the pan half way with water, place the mirror in the water, making sure it is sideways; point your flashlight toward the mirror, place the white paper exactly above the mirror, and finally adjust the angle of the paper until the rainbow appears. Voila, you have just created your own rainbow without waiting for raindrops or sunlight. However, nothing compares to the beauty of the real one, spreading its wings across the sky in full glamor.
References
poets.org
englishclub.com
telegraph.co.uk