Many people use the terms “purple” and “violet” interchangeably. From a scientific perspective, there is a distinction between these two hues. While both colors appear similar to the human eye and are situated between blue and red on the color wheel, their origins in the light spectrum differ. This article explores the scientific definitions of violet and purple, clarifying why they are not identical.
Violet: A Color of the Spectrum
Violet is a spectral color, meaning it exists as a distinct band within the visible light spectrum. It is a pure color with its own specific wavelength, making it a fundamental component of a rainbow or light dispersed through a prism. The visible light spectrum, often remembered by the acronym ROYGBIV, includes red, orange, yellow, green, blue, indigo, and violet. Violet is positioned at the shortest wavelength end of this visible spectrum, just before ultraviolet light.
The wavelength range for violet light is approximately 380 to 450 nanometers (nm). Isaac Newton identified violet as one of the seven colors when he divided the spectrum of visible light. When violet light strikes the retina, both the blue and, to a lesser extent, the red cone cells are activated, which the brain interprets as violet.
Purple: A Perceived Color
In contrast to violet, purple is considered a non-spectral color, meaning it does not have its own unique wavelength on the visible light spectrum. Purple is a perceived color created by the brain when a combination of red and blue light, or pigments, are mixed. For instance, on computer and television screens, purple colors are formed by mixing red and blue light using the RGB color model.
Artists commonly create purple by mixing red and blue pigments, such as in paints or dyes. This blending allows for a wide range of purple hues, which can lean more towards red or blue depending on the proportions of the mixed colors. Purple bridges the visual gap between the red and violet ends of the spectrum, forming a continuous color wheel.
Understanding the Distinction
The key distinction lies in their physical nature: violet is a pure spectral color with a defined wavelength, while purple is a composite color, a perception created by mixing red and blue light or pigments. While violet is found naturally in phenomena like rainbows, purple is not present in the rainbow because its constituent red and blue wavelengths are separated.
Despite this scientific difference, violet and purple are often used interchangeably in everyday language due to their similar appearance. Violet tends to be a bluer shade, while purple often appears more reddish. In fields like physics, the distinction is precise, referring to specific wavelengths, whereas in art and common usage, “purple” encompasses a broader range of hues between red and blue, including shades that might be scientifically classified as violet.