HW2S10Modern Physics_solstud

# Modern Physics

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HW2 Problem 1: Blackbody Radiation The Sun radiates approximately as a blackbody at a temperature of about 6000[K]. a) How much energy is emitted per square centimeter per second in the range of wavelengths from 579 [nm] to 581 [nm]? b) What is the total power radiated by the Sun? c) Assuming that this energy is produced by chemical processes and that the mass of the Sun is 2*10 30 [kg], how long would you estimate the Sun could burn? Are you assuming that it keeps burning at 6000[K]? Is this assumption reasonable? 1 8 _ ] [ 10 02 . 0 ] [ 581 ] [ 579 3 2 14 kT hf e hf c f u ity energydens Hz nm c nm c f a) ] [ 10 3 . 8 14 . 4 6000 10 38 . 1 10 17 . 5 10 63 . 6 _ _ _ _ _ 2 5 23 14 34 3 s m J fc u kT hf f h with above as same fc u energyperm f u b) ] [ 10 47 . 4 ) 10 96 . 6 ( 4 6000 10 67 . 5 1 26 2 8 4 8 W P c) In a chemical process, 1 kg can yield several 10 3 cal or ~ 10 7 [J/kg] and Sun has 2*10 30 [kg] 4*10 10 [s] ~10 3 years T would decrease as fuel depletes, so T=const is an unreasonable assumption.

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HW2S10Modern Physics_solstud - HW2 Problem 1 Blackbody...

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