4-27 The equation of state for radiant energy in equilibrium with the temperature of the walls of a cavity of volume Vis P = aT*/3. The energy equation is U = aT'V. (a) Show that the heat supplied in an isothermal doubling of the volume of the cavity is 4a T* V/3. (b) Use Eq. (4-3) to show that in an adiabatic process IT is a constant.\f