Consider a spherical shell of radius R at temperature T. The black body radiation inside it can be considered as an ideal gas of photons with internal energy per unit volume u=VU∝T4 and pressure p=31(VU) . If the shell now undergoes an adiabatic expansion the relation between T and R is:
Held on 4 Apr 2015 · Verified 6 Jul 2026.
T∝R31
T∝e−R
T∝e−3R
T∝R1
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