What people refer to as “light” can be regarded from the physical perspective as a particular range of frequencies within the electromagnetic spectrum. This range is called the visible spectrum. Everything we see is made of waves within this range emitted or reflected by objects. The spectrum consists of colors from red (the lowest frequency) to violet (the highest frequency) and can be observed when a ray of light is cast at an angle on a transparent object like a prism or a water drop. The visible spectrum was discovered in the 17th century and studied throughout the late 18th and early 19th centuries as technology advanced, and today knowledge of the visible spectrum has found use in many areas of human activity.
Long before a physical explanation was proposed, people could observe the disassembling of white light into the visible spectrum colors under natural conditions. They could see rainbows in the sky and a varicolored glow over a flow of water drops (for example, when watering plants). The term “spectrum” was coined by Isaac Newton in 1671. Newton also recognized the seven primary colors of the spectrum, suggesting that the light of different colors travels through prisms at different speeds (McLaren, 1985). Since then, debate has been ongoing regarding the number of primary colors. In particular, many claim that indigo should not be included in the list. McLaren (1985) argues that what Newton meant by “indigo” was blue, while “blue” is what people nowadays would refer to as cyan.
Understanding of the visible spectrum was augmented in the beginning of the 19th century. Electromagnetic radiation with a frequency below red (infrared) and above violet (ultraviolet) was discovered and studied. In 1802, Thomas Young experimentally measured the wavelength of different colors within the spectrum (Brand, 1995). The visible spectrum was established to be a range within the electromagnetic spectrum. Later, however, experiments showed that some animals can see light that humans cannot (Cuthill et al., 2000). In other words, particular limits of the visible spectrum are species-specific.
There are many applications for the visible spectrum concept in different areas of technology and science. For example, present-day monitors are designed based on the understanding of spectrum continuity and differences in wavelength (Spiker, 2011). Combining primary colors allows humans to see numerous colors on screens. Another example is the use of infrared radiation. The technology of infrared photography captures and visualizes the light that is invisible to the human eye. This technology is used for medical purposes (finding tumors), military purposes (detecting hidden forces and weapons), and in astronomy (observing faint stars). But the most extensive area of visible spectrum use is spectroscopy, which pertains to the exploration of characteristics of distant objects by analyzing the electromagnetic radiation they emit or reflect. According to Brand (1995), our knowledge of outer space and the universe in general is largely gained through spectroscopy.
The discovery of the visible spectrum was one of the most important and fundamental events in optics, the science of light. The study of the visible spectrum has significantly contributed to spectroscopy, a method of exploring the universe based on the knowledge of how different objects, surfaces, materials, and environments interact with electromagnetic radiation. Moreover, applications of the visible spectrum extend to many other areas like medicine, astronomy, computer science, and military operations.
References
Brand, J. (1995). Lines of light : The sources of dispersive spectroscopy, 1800-1930. Sydney: Gordon and Breach.
Cuthill, I. C., Partridge, J. C., Bennett, A. T., Church, S. C., Hart, N. S., & Hunt, S. (2000). Ultraviolet vision in birds. Advances in the Study of Behavior, 29(1), 159-214.
McLaren, K. (1985). Newton’s indigo. Color Research & Application, 10(4), 225-229.
Spiker, N. (2011). Reproducing Visible Spectra. Web.