A Slide Rule for Radiation Calculations

A slide rule has been developed to facilitate rapid calculations based on the Planck radiation formula. Quantities such as the radiant flux density in a given wave‐length region, the spectral radiant flux density at a given wave‐length, or the corresponding quantities expressed in photon units, can be obtained readily for a black body over a range λT=2×102 to λT=4×106 micron degrees with an accuracy of about 1 percent. Simple extension rules can be used for larger values of λT.