function I=planck2(par,l)
% I=planck2(par,l)
%
% Planck's radiation law gives spectral intensity I for a
% radiation field of temperature T.
%
% par(1)=T in K
% par(2)=arb norm factor
% l=wavelength in meters
% Output in arb units

T=par(1);
norm=par(2);

h=6.626e-34;
k=1.38e-23;
c=3e8;
x=(h*c)./(k*T*l);

I=norm*(2*h*c^2*l.^-5)./(exp(x)-1);
