Unformatted text preview: The solution to Problem 1 of our midterm exam is covered in the following subsection of my notes on radiation transport. 4.3 Emission and absorption lines We already noted that in thermodynamic equilibrium the emission spectrum should be a Planck ian, B ν ( T ) and the matter will also follow a thermal Maxwellian with temperature T . In many cases we find that the Maxwellian describes the particles well, but the radiation field is not a Planckian at the same temperature T . In such a situation the matter is said to be in Local Thermodynamic Equilibrium (LTE). In LTE, the source function is still a Planckian, and in the absence of scattering we have j ν = α ν S ν = α ν B ν ( T ) (4 . 25) Specifying j ν now boils down to specifying T ( ~x ), provided α ν is known. If no background source of emission exists, the solution to the radiation transport equation for a homogeneous medium is I ν ( τ ) = B ν ( T ) [1 exp( τ )] (4 . 26) How would a composite of continuum emission and spectral lines look like? If more than oneHow would a composite of continuum emission and spectral lines look like?...
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This note was uploaded on 02/29/2012 for the course PHYS 227 taught by Professor Rabe during the Fall '08 term at Rutgers.
 Fall '08
 RABE
 Physics, Radiation

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