Types

• Light is a form of electromagnetic radiation, so all light particles or photons have both wavelength (the distance from wave crest to wave crest) and frequency (the number of waves that pass a given point in one second). Wavelength and frequency are related by the following equation, speed of light = frequency x wavelength. What our eyes perceive as different colors of light are merely different wavelengths of electromagnetic radiation.
  
  

Function

• When a photon of light passes through the lens of your eye, it may strike a type of light-sensitive cell called a cone. When it does so, it will be absorbed by a membrane-embedded pigment called a photopsin. There are three types of photopsins in your eye, each of which has a slightly different molecular structure and preferentially absorbs light in a given range of wavelengths.
  
  

Considerations

• Some of the cones in your eyes have the red-absorbing photopsin, others the green-absorbing photopsin and others the blue-absorbing photopsin, so light of a given wavelength will stimulate some cones more than others. The range of wavelengths absorbed by the three types of photopsins overlap, so your brain distinguishes intermediate colors based on which type of cone receives more stimulation. If both the red and the green cones are stimulated, for example, your brain might perceive the light as yellow or orange, depending on which type of cone receives the most stimulation.