A Guide to Physics Problems. Part 2. Thermodynamics, Statistical Physics, and Quantum Mechanics

184 SOLUTIONS

where is the Stefan–Boltzmannconstant. Only afraction of

this flux reaches the Earth. In equilibrium this fraction equals the total

flux radiatedfrom theEarth at temperature So

From (S.4.73.2) weobtain

b) The radiation pressure on theEarth isgiven by

where is the ratio of the total fluxfrom the Sun to thefluxthat

reaches theEarth. Theradiationforce on the Earth

where is thecrosssection of theEarth.

c) For the small “chondrule” the temperature will be the same because it

depends only on the angle atwhich the Sun isseen and theradiationforce:

d) Using (S.4.73.3) anddenoting the meltingtemperature of themetallic

particle and the distance from the Sun we obtain