Q:  What are the units of mean intensity?


       The units must be the same as those of specific intensity,
       except for the "per steradian".   Therefore,

 
                  Joules
           -----------------------
               s * m^2 * m 

       
       where the "m^2" refers to the area of the plate (dA), and the
       next term "m" refers to the range of wavelengths (d lambda).
 
       We can combine these terms to yield


                  Joules                          ergs
           -----------------------   or     -----------------
                 s * m^3                       s * (cm)^3 
 


       Of course, since radians and steradians aren't "really" units,
       these units are in many ways exactly the same as those
       for specific intensity.  

       This means that the blackbody function can be described 
       as a mean intensity, too.