O n t h e T r a c k o f M o d e r n P h y s i c s

1. Red White light Orange Yellow Green Glass prism Blue Violet O n t h e T r a c k o f M o d e r n P h y s i c s See, to believe The human eye is rather blind, compared to the ear: it senses only one octave of frequencies (380-760 nm) compared to 8 octaves of the ear (50-20000 Hz). But it is well adapted to our Star emission spectrum. The easiest spectroscopy is the optical one. If you see you believe! UV VIS NIR First systematic investigations of spectra were done by Bunsen and Kirchhoff between 1855 and 1863. http://physics.kenyon.edu/EarlyApparatus/Optics/Spectrometers/Spectrometers.html By optical observations, new elements, like rubidium, purple -shining in flame, or neon, were discovered. Spectrum of the Solar Radiation: UV- ultraviolet, VIS- visible radiation, NIR – near infrared Adapted from:http://eetd.lbl.gov/coolroof/intro.htm, Lawrence Berkeley NL, USA To see a spectrum, anything is good: “chromatographic” glasses, professional spectro- meter or even a CD-grating. That of hydrogen, is the simplest with only 4 lines in the visible range. But they were so important for quantum mechanics… The human eye is adapted to the Solar spectrum: rods are most sensitive in its maximum The spectrum of the 10-electron atom, neon, is already quite complicated. Neon flashes in red, but its spectrum contains green and blue, as well. The human eye posses two types of receptors: rods for black and white vision and cones for colours, with three types of spectral sensitivity. Optical spectroscopy can be divided into:emission,absorption, and fluorescence. What is the “real colour” , is not a trivial question. 11-Cis Retinal is a molecule bent at 90º. When illuminated, it stretches along, forming a chain. Another pigment, rho-dopsin serves for the black/white vision. This graphic was produced by Rajeev Narayan The Joy of Visual Perception: A Web Book Peter K. Kaiser, York University  http://www.yorku.ca/eye/   Emission spectrum of the “energy-saving” fluorescent lamp Absorption and fluorescence spectrum of an ice-cream spoon Our vision is different than that of honey-bees [1]. They react best to monochromatic patters, in particular to the yellow but posses also receptors of ultraviolet (with maximum efficiency at 344 nm). Bees see by the contrast with the green and ignore the brown colour. What we see, we believe. But even if we do not see, we must believe. What is above the visible light, we call under-red, what is below: above-violet. [1] Silke Stach, Julie Benard and Martin Giurfa, Local-feature assembling in visual pattern recognition and generalization in honeybees, Nature 429, 758-761 ( 2004) You can not see the infrared but your digital camera can. You do not feel ultraviolet, but these plastics (and Your skin) does. Goethe and Newton wrote treaties about colours. Colours are different for snakes and bees. For You, they are Your own. Just paint! 1/2