Physics
Visible Spectrum
Quick fact
The human eye can distinguish about 10 million different colors, yet the visible spectrum is less than 1% of the entire electromagnetic spectrum.
Why this is interesting
You see a rainbow and name its colors, but did you know the colors you see are only a tiny slice of all the light that exists? Why are we blind to the rest?
Read the full explanation
Understanding Visible Spectrum
Light is a wave, and its color depends on its wavelength—the distance between successive wave peaks. The visible spectrum is the range of wavelengths our eyes have evolved to detect, roughly from 380 nm (violet) to 700 nm (red). Shorter wavelengths (ultraviolet) and longer ones (infrared) are invisible to us. When white light passes through a prism, it spreads into a continuous band of colors—red, orange, yellow, green, blue, indigo, violet—each corresponding to a different wavelength. Our eyes contain specialized cells (cones) that are sensitive to different parts of this range, allowing us to perceive color.
A deeper explanation
The visible spectrum's boundaries are not arbitrary—they are determined by two key factors: the transparency of Earth's atmosphere and the evolutionary history of our species. The atmosphere blocks most UV and much infrared, but it transmits visible light efficiently. Early organisms that could detect this light gained advantages in finding food, avoiding predators, and navigating. Over millions of years, our eyes optimized for this 'optical window.' Within the visible range, each wavelength stimulates one or more of three types of cone cells in the retina, enabling trichromatic color vision. This mechanism also explains why some animals see different spectra: bees see UV, snakes sense infrared. The visible spectrum is thus a beautiful intersection of physics—the properties of light—and biology—the design of our visual system.