function I_lambda=black_body_radiation(lambda,T)
% black body radiation spectrum
% lambda - wavelength of EM wave
% T - temperature of a black body
h=6.626e-34;  % Plank constant
c=2.998e8;    % speed of light
k=1.380e-23;  % Boltzmann constant

I_lambda = 2*h*c^2 ./ (lambda.^5)  ./ (exp(h*c./(lambda*k*T))-1);
end
