Our perception of the world is deeply intertwined with the colors we see. Human vision, while sophisticated, captures only a small fraction of the vast electromagnetic spectrum. This suggests a world of “colors” exists beyond our immediate perception, extending far beyond what our eyes can detect.
Our Visible Spectrum
Color, in scientific terms, is our brain’s interpretation of different wavelengths of light within the electromagnetic spectrum. Light is a form of electromagnetic radiation; its various forms, including radio waves, microwaves, and X-rays, differ in their wavelengths. The human eye is equipped to perceive a specific range of these wavelengths, translating them into the vibrant array of colors we experience.
This narrow band is known as the visible light spectrum. For humans, this spectrum spans wavelengths from approximately 380 to 750 nanometers (nm). Violet light has the shortest wavelengths, around 380 nm, while red light occupies the longest, extending to about 700-750 nm. When white light passes through a prism, these wavelengths separate, revealing the continuous spectrum of colors we commonly associate with a rainbow.
Beyond the Visible
Beyond our visible spectrum lie forms of light imperceptible to the human eye. Two prominent examples are ultraviolet (UV) light and infrared (IR) light. Ultraviolet light has wavelengths shorter than violet light, ranging from 10 to 400 nm. This invisible light is a component of sunlight, responsible for causing sunburns and tans. Artificial sources of UV light include tanning beds and specialized lamps for disinfection or fluorescent effects.
Infrared light, on the other hand, consists of wavelengths longer than red light, extending from approximately 780 nm to 1 millimeter. While humans cannot see infrared light, we often perceive its effects as heat. Common applications of infrared technology include television remote controls, which use IR signals, and thermal imaging cameras, which detect heat. Heat lamps also rely on infrared radiation.
Why We Have Visual Limits
The limitations of human vision stem from specialized photoreceptor cells in our eyes: rods and cones. Rods are highly sensitive to low light levels, responsible for night vision and perceiving shades of gray. Cones are activated by brighter light and are essential for color vision.
Humans possess three types of cone cells, each tuned to different wavelengths: short (blue), medium (green), and long (red). These cones contain proteins called photopsins, which absorb specific wavelengths, allowing us to perceive a wide range of colors by combining their signals. Our eyes simply lack the specific types of photoreceptors or sensitivity to detect light outside this range, such as ultraviolet or infrared wavelengths. These visual limitations are a product of evolution, as our vision developed to perceive the light spectrum most relevant for survival in our particular environment.
Variations in Color Perception
Color perception is not uniform across all individuals or species. Within the human population, some individuals experience color vision deficiency, often referred to as “color blindness.” This condition typically arises from variations in the functionality of one or more of the three types of cone cells in the retina. While very few people are completely unable to see any color, common forms, such as red-green color deficiency, make it difficult to distinguish between certain shades.
The animal kingdom offers diverse visual capabilities, illustrating how other creatures perceive parts of the spectrum invisible to us. Bees, for instance, can see ultraviolet light, which helps them locate nectar guides on flowers unseen by humans. Snakes, particularly pit vipers, possess specialized heat-sensing organs that allow them to detect infrared radiation emitted by warm-blooded prey, effectively ‘seeing’ in the dark. Some fish, like goldfish, are even capable of perceiving both ultraviolet and infrared light.