% Black Body Radiation
% Plank's Black Body Radiation Law
% --------------------------------

clear;clf;clc;

% Input Wavelengths

wl=logspace(-1.5,2);   		% microns

% Input Equation Constants

C1=3.741*1e4;					% w*cm^-2*micron^4
C2=1.438*1e4;					% micron*deg K

% Compute Spectral Response

T=[6000 4000 2000 1000 ];  % deg Kelvin
for i=1:4;
   Tx=T(i);
   a=exp(C2./(wl*Tx))-1;
   W=C1./(a.*wl.^5);
   Wx(:,i)=W';
end;

% Compute Spectral Response for Low Temperatures

wl1=logspace(0,2);			% microns
T1=[500 300];

for j=1:2
  Tx1= T1(j); 
  a1=exp(C2./(wl1*Tx1))-1;
  W1=C1./(a1.*wl1.^5);
  Wx1(:,j)=W1';
end;

% Plot Spectral Response

loglog(wl,Wx,'k');grid;
xlabel('Wavelength - microns');
ylabel('Spectral Power Density - w/cm^2-micron');
axis([.01 100 1e-5 1e5]);
title('Power Spectral Density 0f Black Body Radiator');
hold on
loglog(wl1,Wx1,'k');