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Unformatted text preview: Since wavelength is easier to measure for light than frequency, one more frequently sees B and I in observational contexts. A graph of B(T ) shows that hotter T 's indeed give both  overall greater intensity everywhere, and  peak at shorter wavelengths. Bλ (T) 2000 K 1750 K 1500 K 1250 K 0 1 2 3 4 λ in µm 5 λ 3.5.3 Asymptotics of the Planck spectrum For h  kT , there is an exponential fall-o in brightness. This is called the \Wien limit." It is why you cannot get a tan under an ordinary incandescent light-bulb: The temperature of its lament is around 2700 K, and so it makes almost no UV. For h  kT the exponential can be expanded h h exp kT 1 = kT +    so that for hv  kT , we have the Rayleigh-Jeans law: 2 B (T )  2c2 kT : ! 45...
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This note was uploaded on 12/29/2011 for the course AST 350 taught by Professor Dion during the Fall '09 term at SUNY Stony Brook.

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