<P> In the 18th century, Goethe wrote about optical spectra in his Theory of Colours . Goethe used the word spectrum (Spektrum) to designate a ghostly optical afterimage, as did Schopenhauer in On Vision and Colors . Goethe argued that the continuous spectrum was a compound phenomenon . Where Newton narrowed the beam of light to isolate the phenomenon, Goethe observed that a wider aperture produces not a spectrum but rather reddish - yellow and blue - cyan edges with white between them . The spectrum appears only when these edges are close enough to overlap . </P> <P> In the early 19th century, the concept of the visible spectrum became more definite, as light outside the visible range was discovered and characterized by William Herschel (infrared) and Johann Wilhelm Ritter (ultraviolet), Thomas Young, Thomas Johann Seebeck, and others . Young was the first to measure the wavelengths of different colors of light, in 1802 . </P> <P> The connection between the visible spectrum and color vision was explored by Thomas Young and Hermann von Helmholtz in the early 19th century . Their theory of color vision correctly proposed that the eye uses three distinct receptors to perceive color . </P> <P> Many species can see light within frequencies outside the human "visible spectrum". Bees and many other insects can detect ultraviolet light, which helps them find nectar in flowers . Plant species that depend on insect pollination may owe reproductive success to their appearance in ultraviolet light rather than how colorful they appear to humans . Birds, too, can see into the ultraviolet (300--400 nm), and some have sex - dependent markings on their plumage that are visible only in the ultraviolet range . Many animals that can see into the ultraviolet range, however, cannot see red light or any other reddish wavelengths . Bees' visible spectrum ends at about 590 nm, just before the orange wavelengths start . Birds, however, can see some red wavelengths, although not as far into the light spectrum as humans . The popular belief that the common goldfish is the only animal that can see both infrared and ultraviolet light is incorrect, because goldfish cannot see infrared light . Similarly, dogs are often thought to be color blind but they have been shown to be sensitive to colors, though not as many as humans . </P>

What is the energy range of visible light