Visible light

Visible light is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 380 to 750 nanometers. In terms of frequency, this corresponds to a band in the vicinity of 430–790 THz.

Overview

The spectrum does not, however, contain all the colors that the human eyes and brain can distinguish. Unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can be made only by a mix of multiple wavelengths. Colors containing only one wavelength are also called pure colors or spectral colors.

Perception of light

Visible wavelengths pass through the eye's cornea and lens and then are focused on the retina, a layer of light-sensitive cells at the back of the eye. The retina contains two types of cells, rods and cones, which are sensitive to different aspects of light. Rods are sensitive to the intensity of light, while cones are sensitive to color.

Color and wavelength

The color of visible light depends on its wavelength. These wavelengths range from 700 nm at the red end of the spectrum to 400 nm at the violet end. Visible light waves are the only electromagnetic waves we can see. We see these waves as the colors of the rainbow. Each color has a different wavelength. Red has the longest wavelength and violet has the shortest wavelength.

Applications

Visible light has a range of applications, including:

• Photography: Visible light is used in photography to capture images.
• Vision: It allows humans and animals to see the world.
• Photosynthesis: Plants use visible light in the process of photosynthesis.
• Communication: Visible light communication (VLC) uses visible light to deliver information.

See also

• Color
• Electromagnetic spectrum
• Light
• Optics
• Photon
• Spectrum

Visible light Resources
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