Midterm Solutions

Page 13 of 16 physics 160 fall 2013 midterm exam 4

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Unformatted text preview: ­8 P/kT To solve for the pressure, use the relation we derived in the homework: dP/dτ = g/κ => Pph = 3/2 GM/R2 1/κ = 3/2 (6.67x10 ­11 N m2/kg2)(1.99x1030 kg)/(6.99x108 m)2 /0.1 m2/kg = 4.07 x 103 N/m2 => nH = (4.07x103 N/m2)/[(1.38x10 ­23 J/K)(5800 K)] = 5.08x1022 m ­3 => nNu = 10 ­8nH = 5.08x1014 m ­3 Page 11 of 16 Physics 160 Fall 2013 Midterm Exam (d) [15 pts] What is the fraction of ionized to neutral Nubulium atoms in the Sun’s photosphere? To simplify the calculation, assume that the partition function for ionized Nubulium atoms Z+ = 1, that all neutral Nubulium atoms are in the n=1 ground state, and that all of the free electrons in the gas come from ionized Nubulium atoms (so N+ ≈ Ne). This is the Saha equation: N+Ne/N0 ≈ N+2/No = 2 Z+/Zo (2πmekT/h2)3/2 e ­ χ/kT Z+ = 1, Z0 = g1 e ­ΔE11/kT = 2, so 2 Z+/Z0 = 1 the numerical factor: 2πmekT/h2 = 2π(mec2)kT/(hc)2...
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This document was uploaded on 02/26/2014 for the course PHYS 160 at UCSD.

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