> Actually, it is all included in the spectrum. Light is just one component of a long and continuous spectrum that includes radio, light, beta, gamma, and other waves. Being a ham makes the entire spectrum very real. > > All that changes is the frequency. Bob - Radiometrically you are correct. - Photometrically you are IMO missing the point. Radiometrically we can measure the wavelength, amplitude, phase, direction, constancy etc of electromagnetic radiation whether it be light, UV, IR by means of it's physical properties (strictly interactions) with other physical things. What we cannot do is actually measure what it looks like. "Pure" monochromatic wavelengths of light (by definition light being the part of the electromagnetic spectrum we can see) are generally seen as coloured (though not the same by everybody - consider synaesthesia. :) ... so there is a one-way relationship. But exactly the same colour ( a perceptual thing ) can be experienced by looking at a mixture of wavelengths, so you simply cannot make the reverse association. Oh let's quote someone else ... the "Color - Enpsychlopedia" http://psychcentral.com/psypsych/Color "Electromagnetic radiation is a mixture of radiation of different wavelengths and intensities. When this radiation has a wavelength inside the human visibility range (approximately from 380 nm to 740 nm), it is called light. The light's spectrum records each wavelength's intensity. The full spectrum of the incoming radiation from an object determines the visual appearance of that object, including its perceived color. As we will see, there are many more spectra than color sensations; in fact one may formally define a color to be the whole class of spectra which give rise to the same color sensation, although any such definition would vary widely among different species and also somewhat among individuals intraspecifically." Colour (as we see it) also is an anomalous beast when it comes to intensity. 1) A mixture of wavelengths that looks bright yellow when viewed at high intensity looks olive green when less intense. Exactly the same mixture of wavelengths - the only physical difference is the total amplitude. The "standard observer" charts attempt to address this but currently only at two points: photopic and scotopic. The "real world" is everything in between as well ... 2) How many colours do you see ? ( Not including white ! ) http://homepage.ntlworld.com/patrick.davies/odd4.htm Explain that with simple physics ... BobT
