Dispersion of light refers to the phenomenon where white light, which is a mixture of different colors, is separated into its individual component colors as it passes through a medium, such as a prism or a droplet of water. This separation occurs because different colors of light have different wavelengths and, consequently, different refractive indices in a medium.
The primary cause of dispersion is the variation in the speed of light in a medium depending on its wavelength. According to the principle of refraction, when light passes from one medium to another (e.g., from air to glass), its speed changes, and its direction is bent. The amount of bending, or refraction, depends on the wavelength of the light.
In a prism, which is a triangular optical element, dispersion occurs as different colors of light are refracted by different amounts when entering and exiting the prism. The result is the spread of colors, forming a spectrum.
The visible spectrum, commonly observed in a rainbow or when white light passes through a prism, consists of the following colors in order of increasing wavelength: violet, indigo, blue, green, yellow, orange, and red (often remembered by the acronym “VIBGYOR”). Each color corresponds to a specific wavelength, and dispersion allows us to see the colors that make up white light.
Dispersion is not only observed in prisms but also in natural phenomena such as rainbows, where water droplets in the atmosphere act as prisms, separating sunlight into its component colors.
One of the notable early experiments demonstrating dispersion was conducted by Sir Isaac Newton, who used a prism to break down white light into its constituent colors, providing crucial insights into the nature of light and color.