Physical Constants

F = 2 h c^{2 -5} / (exp(hc/kT) - 1).

or, combining the constants:

F = c₁ ^-5 / exp(c₂ /T) - 1),

where c₁ = 2 hc² = 3.7419  × 10^-5 erg cm² s^-1 [ in cm]
and c₂ = hc/k = 1.4288 cm °K.

In these equations, the physical constants used are:

= 3.14159
c = 2.9979  × 10¹⁰ cm/s (the speed of light)
h = 6.6262  × 10^-27 erg s (Planck constant)
k = 1.3806  × 10^-16 erg deg^-1 (Boltzmann constant)
= 5.67   × 10^-5 erg cm^-2 s^-1 K^-4

The variables are:

T the temperature in degrees Kelvin (Centigrade degrees above absolute zero)
the wavelength in cm.