Rainbow Formation

A new study completed at Penn State University discovered a different way that rainbows can form. Rainbows form when light hits droplets of water, and light is reflected. First, the average speed of light slows down when traveling through a medium, but the change in speed will depend on the size of the medium. Higher frequencies will travel slower than lower frequencies, and blue light will bend more than red light. Next, when white light enters a medium, the light is bent and is separated into colors depending on frequency. Finally, white light separates, which thus creates a rainbow. Because of the different wavelengths in the electromagnetic spectrum, light bounces off at different angles, which thus separates the spectrum and creates a rainbow. However, this study concluded that rainbows may also form because water droplets that condense and hang from underneath a petri dish lid. Before emerging near one edge, light waves will enter the other edge of a droplet, and bounce two or more times off a dome of the droplet, similar to how light reflects off the back on a raindrop when creating a rainbow. In this study, which took place in 2017, micron-sized spherical droplets contained two types of oil. The lighter colored oil formed a round shaped upper layer that researchers intended to use as a lens. However, when lit from above, the edges glowed with color that could be seen at the angle at which they were viewed, and also depended on their size. Different colors that were seen are a result of changing the size of water droplets. After reading this article, I was able to understand the meaning of iridescence. Iridescence refers to the different colors reflected at different angles, when white light is separated into its constituent colors. Iridescence may occur from refraction, the bending of light, as well as diffraction, which is when light reflects off a more complicated structure. Finally, at the end of the study, it was concluded that iridescence emerges through a new mechanism that blends new properties of previous elements together.