Final answer:
The free energy of a photon gas can be determined by integrating the equation for pressure with respect to temperature.
Step-by-step explanation:
The free energy of a photon gas can be determined by integrating the equation for pressure with respect to temperature. The equation for pressure is given as P = 1/4αT³, where α is the constant. The free energy, F, is given by the equation F = -∫P dT. Integrating the equation for pressure gives F = -1/12αT⁴. Therefore, the correct option is d. F = - (1/4αVT³).