Role of refractive index, a material property, in the formation of rainbows, diffraction, and inference fringes

Abstract

One of the prominent material properties of an optical material is the refractive index. It is the only property that governs various naturally occurring spectacular phenomena such as the formation of a rainbow, color dispersion during sunrise and sunset, and many more. The diameter of a rainbow is characterized by the refractive index of the droplets of water. The calculation of how often an illuminated ray refracts through one medium to the next (for example, from air to water) is determined by a refractive index. A high refractive index droplet helps create a smaller radius of a rainbow. For example, rainbows produced by seawater are less than plummeting rainbows, and saltwater has an improved refractive index than freshwater. Experiments in the classroom arouse new ideas, questions and contribute to developing clarity on Principles of Physics. In this paper, we explore the importance of the material property, refractive index demonstrating dispersion by creating rainbow spectrum, diffraction, and interference fringes in the classroom utilizing the tools available in a laboratory are presented. The experiment on Rainbow makes students observe a well-defined spectrum caused by white light undergoing dispersion through a prism. The experiment on Diffraction and double-slit Interference makes use of locally handmade slits exposed to Sodium lamps to produce fringes. Method to determine the wavelength of light is presented. When performed in the classroom, a variety of questions were posed by students leading to peer interaction and presentation of their ideas.