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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

Reflection from snow does not produce colors, but reflection inside ice crystals does. CD-cover “produces” colors, but usually reflecting polarized light, i.e. from blue sky. Unless, the poly- mer is strongly oriented, like here. Reflection in azzure on borders of

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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

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  1. Reflection from snow does not produce colors, but reflection inside ice crystals does. CD-cover “produces” colors, but usually reflecting polarized light, i.e. from blue sky. Unless, the poly- mer is strongly oriented, like here. Reflection in azzure on borders of the gold-doped, red ash-tray come from Mie scattering, like in the sky. Look carefully or snap shots: spectra are everywhere. This is Red See. In the left image no dark blue is present, in the right image no yellow but a lot of red. One is of so-called energetic lamp, one of the morning sky. Can You guess which is which? Colors in CD-cover are complemen- tary, obtained by subtraction of red, blue or green from white. Separating colors can be done by refraction, like here, diffraction, like to the right, or scattering. 108 5 H OH 2 5 H COOH 107 CO-OC 2 C 3 3 CH 3 CH OH CO-OCH 106 CHO 3 3 CH -CO-CH 3 3 CH CH 105 3 cps CH 104 103 102 10 40 60 80 100 m/e 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 Spectroscopy or ghost science Carmem A. Busko Carmem A. Busko Carmem A. Busko Look! how blue can be different! All difficult words come from Greek. All, but “spectrum”. First used by Cicerone, in Italian means spettro (=ghost), simulacro (= figure or sculpture). Spectroscopy deals with images: a colourful rainbow, a sunset or just the cloudy sky. In other words: spectrum is a ghost and Spectroscopy - a science on ghosts. And then, also red is different! Spectrum is an image, something produced by the object, like the reflected or emitted light. Then You need an analyser, to show single components. This can be a prism, a diffraction grate, but also a snow crystal or a CD-cover. Separated colours, like in a CD form a spectrum. So, separating features of an object is to makea spectrum. This can be the mass of positive ions in strawberries smell, the energy of photons from an annihilating antimatter, faint hints in the energy dependence for muon production or infrared absorption by silicon. All these, we call spectra. And all are so beautiful for scientists, as a purplemorning sky. Hoping, also for You! Three upper sky photos are by Carmen Busko, Sao Paolo, Brazil, thanks! http://www.trekearth.com/gallery/South_America/Brazil/photo89543.htm Remaining photos are by GK. 1/1

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