where R is called spectral radiance intensity (energy/unit time/unit surface
area/unit solid angle/unit wavelength) in unit of watt/(m2.sr.m)
while a, b are constants given by
13
1
( , ) 1 5 /
eb T
R T a
a 2c2h : h Plank constant 6.626x10-34 J.s
: k Boltzmann constant 1.381x10-23 J/K
k
b hc
c 3x108 m/s : Velocity of EM wave in vacuum