Homework 4 Solutions

70 y 028 and z 002 compute the density at the

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Unformatted text preview: 0 3 270 m/s2 ≈ = P= = 2700 N/m2 2 /kg dτ 2/3 − 0 2 0.1 m => P = 1800 N/m2 (c) [5 pts] Assume that the photosphere is a mostly neutral ideal gas with X = 0.70, Y = 0.28 and Z = 0.02. Compute the density at the photosphere for Tphot = Teff = 5800 K. Note: you will need to first derive the proper mean molecular weight µ. From Eqn. 10.14, 1/µ = X + 0.25Y + <1/A>Z = 0.77 for a neutral gas From the ideal gas relation: P= ρkT P µmH ⇒ρ= µmH kT (1800 N/m2 )(1.67 × 10−27 kg) = (0.77)(1.38 × 10−23 J/K)(5800 K) = 4.9x10 ­5 kg/m3 (d) [5 pts] The primary source of opacity in the Sun’s (and other cool stars’) atmosphere is H ­ opacity, which arises when a neutral Hydrogen atom becomes slight polarized in the presence of a free electron, resulting in a weak (χ = 0.754 eV) bound state. Assuming that this is the sole source of opacity, calculate κH ­ from equation 9.28 for the conditions de...
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This document was uploaded on 02/26/2014 for the course PHYS 160 at UCSD.

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