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Astrophysics/photon energy of a blackbody spectrum

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Expert: - 8/27/2008


Question
The approximate mean photon energy of a blackbody spectrum which is emitted by an object at a temperature of 10^5 K will be ? eV? This was a question asked at a pub quiz recently, and no one had a clue what the answer could be. In fact most of us had no idea what this meant. Could you help?

Answer
There are two different things here.  The average energy of a blackbody photon is 2.7 kT where T is the absolute temperature and k is Boltzmann's constant.  The peak wavelength is given by 2.898*20^-3/T in meters, which can be used to calculate the *peak* energy output wavelength (which is what physicists are usually concerned with).  Which were they asking?  Average or peak?

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Steve Nelson

Expertise

Fusion, solar flares, cosmic rays, radiation in space, and stellar physics questions. Generally, nuclear-related astrophysics, but I can usually point you in the right direction if it's not nuclear-related or if it's nuclear but not astrophysics.

Experience

Currently a physics professor at the University of Texas of the Permian Basin. Doctoral dissertation was on a reaction in CNO-cycle fusion, worked in gamma-ray astronomy in the space science division of the naval research laboratory in the high-energy space environment branch.

Organizations
Physics professor at the University of Texas of the Permian Basin.

Education/Credentials
Ph.D. in physics, research was on nuclear fusion reactions important in stellar fusion.

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