Above 10-to-the-7 kelvins, this quantity approximately equals 0.2 times the quantity “one, plus the hydrogen mass fraction.” [read slowly to end of sentence] The reciprocal of a form of this quantity is given by the frequency average of its reciprocal, weighted by the temperature partial derivative of the Planck distribution, “B sub nu.” For bound–free and free–free processes, this quantity is proportional to density times temperature to the negative seven-halves power, according to Kramers’s law. (10[3])As this quantity changes, the oscillation of the partial ionization zone drives the luminosity fluctuations (10[2])of variable stars (10[1])in the kappa mechanism, where kappa denotes (10[1])this quantity. (-5[1])The integral of this quantity (10[1])with respect to vertical position is the optical depth. For 10 points, what quantity measures the intensity (-5[1])lost (-5[1])by radiation (10[1]-5[1])traveling (10[1])through a star? ■END■ (10[6]0[9])