You have a metal cavity with a small hole in it.  You send electromagnetic radiation through the hole and calculate that the amount of standing waves in the box is proportional to the inverse fourth power of wavelength.  
You have a metal cavity with a small hole in it.  You send electromagnetic radiation through the hole and calculate that the amount of standing waves in the box is proportional to the inverse fourth power of wavelength.  Then you figure that the radiance from the hole will be proportional to the number of standing waves.  Your formula works OK at shorter wavelengths, but gives catastrophic results for energies above the visible spectrum.  FTP, name this law that was corrected by Planck, the breakdown of which caused the ultraviolet catastrophe in blackbody radiation.
You have a metal cavity with a small hole in it.  You send electromagnetic radiation through the hole and calculate that the amount of standing waves in the box is proportional to the inverse fourth power of wavelength.  
Rayleigh-Jeans formula