Consider a transmission line of length L on which electromagnetic waves satisfy the one-dimensional wave equation = v2∂2E/∂x2 = ∂2E/∂t2, where E is an electric field component. Find the heat capacity of the photons on the tine, when in thermal equilibrium at temperature τ. The enumeration of modes proceeds in the usual way for one dimension: take the solutions as standing waves with zero amplitude at each end of the line.