Calculate the number of photons in 10³ L of radiation in thermal equilibrium at 500 K.
a) 4.34 x 10¹⁵5 photons
b) 4.34 x 10¹⁵ photons
c) 2.52 x 10¹⁵ photons
d) 2.52 x 10¹⁵ photons