on a visible spectrum scale what are the numbers for the colors of ROYGBIV? for example is violet 400-500nm and red is 700-800nm? how about the other colors? If the energy of a photon is 2.63 x 10^-19 J, how can we tell what color this is? i was looking at this electromagnetic spectrum and it doesnt help me much. http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html help!