Saylor URL: http://www.saylor.org/books Saylor.org
Light waves with shorter frequencies are perceived as more blue than red; light waves with higher intensity are
seen as brighter.
In his important research on color vision, Hermann von Helmholtz (1821–1894) theorized that
color is perceived because the cones in the retina come in three types. One type of cone reacts
primarily to blue light (short wavelengths), another reacts primarily to green light (medium
wavelengths), and a third reacts primarily to red light (long wavelengths). The visual cortex then
detects and compares the strength of the signals from each of the three types of cones, creating