I understand Spectral Emissive Power as the total amount of energy carried by photons having the same wavelength (energy), and it has the unit of (W/m2.um).
I could not grasp the physical significance of diving energy over wavelength (um). Dividing energy over area means flux, dividing energy over time signifies rate (power). What does it mean to divide Energy on wavelength?!
So, what I concluded so far is that including the wavelength unit in the Spectral Emissive Power unit is a probabilistic concept. In other words, the Planck's Distribution is a Probability Distribution (How probable a photon will have a certain wavelength). Of course, most photons will most probably have the Wien Wavelength (Peak Wavelength).
For now, this understanding makes sense to me. Kindly correct me if I'm wrong.