What are the units for spectral energy density according to the Planck Law?

[Fr34k]

I will just paste the link, cause its faster this way:

http://scienceworld.wolfram.com/physics/PlanckLaw.html

The last equation for spectral energy density if you look at the units you get eVs/m^3 or Js/m^3, yet energy density is supposed to be J/m^3. What am I missing here?

 

[mfb]

It is a density per frequency (and space). To get the total (spatial) energy density, you have to integrate over the whole frequency range (0 to infinity).