MATLAB: Integrate planck function between two intervals

numerical integrationplanck law

function Planck_law
c1=27.742*10.^8;
c2=1.43878*10.^4
sigma=5.67*10.^-8
T=5780
lamda_1= 8
lamda_2= 13
fun= @(lambda,sigma,c1,c2,T) c1./lamda.^5.*(exp(c2./(lamda * T))-1);
F = integral(fun,lamda_1,lamda_2,0.001)./(sigma.*T^4)
This code shows error "Expected a string scalar or character vector for the parameter name, instead the input type was 'double'.

Best Answer

Check this code and compare it with your code to see the mistakes.
c1 = 27.742*10.^8;
c2 = 1.43878*10.^4;
sigma = 5.67*10.^-8;
T = 5780;
lamda_1 = 8;
lamda_2 = 13;
fun = @(lambda) c1./lambda.^5.*(exp(c2./(lambda * T))-1);
F = integral(fun,lamda_1,lamda_2)./(sigma.*T^4)
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