# Plot the Planck's Radiation curves Below

11 views (last 30 days)
Tunde Adubi on 18 Sep 2022
Edited: Torsten on 19 Sep 2022
I tried to plot both radiation curves attached using Planck's and wien's equation as shown below.
Can you help correct this?
%---------Black Body Radiation Using Planck's Equation
%---------Black Body Radiation Using Wien's Equation
clc;
close all;
clear all;
%-----------------------------------%
c=3*10^8; % speed of light in vaccum
h=6.625*10.^-34; % Planck constant
k=1.38*10.^-23; % Boltzmann constant
T=(300); % Temperatures in Kelvin
V= (0:5:30).*1e2; %The wavenumber(Hundred)
Lam=1./V; %The wavelength
figure(1)
%------------Wiens equation
I300= ((2*h*c*c*(V.^3))./(exp(h*c.*V)./(k*T))-1);
%------------Plancks equation
I2(:,T)=(2*h*c*c)./((Lam.^5).*(exp((h.*c)./(k*T.*Lam))-1));
%-----------------------------------------------------
plot(V,I300,'k','linewidth',1)
hold on
plot(Lam,I2(:,T),'r','linewidth',1)
xlabel('Wavenumber','fontsize',14)
ylabel('Spectral Irradiance [W m^{-2} sr^{-1} nmm^{-1}]','fontsize',14)
fh = figure(1);
set(fh, 'color', 'white');

Torsten on 18 Sep 2022
x-axis and y-axis for the two plots have very different scales. So there must be an error in your formulae if we compare it to the .png file you attached.
%---------Black Body Radiation Using Planck's Equation
%---------Black Body Radiation Using Wien's Equation
clc;
close all;
clear all;
%-----------------------------------%
c=3*10^8; % speed of light in vaccum
h=6.625*10.^-34; % Planck constant
k=1.38*10.^-23; % Boltzmann constant
T=(300); % Temperatures in Kelvin
V= (0:5:30).*1e2; %The wavenumber(Hundred)
Lam=1./V; %The wavelength
figure(1)
%------------Wiens equation
I300= ((2*h*c*c*(V.^3))./(exp(h*c.*V)./(k*T))-1);
%------------Plancks equation
I2=(2*h*c*c)./((Lam.^5).*(exp((h.*c)./(k*T.*Lam))-1));
%-----------------------------------------------------
figure(1)
plot(V,I300,'k','linewidth',1)
xlabel('Wavenumber','fontsize',14)
ylabel('Spectral Irradiance [W m^{-2} sr^{-1} nmm^{-1}]','fontsize',14)
figure(2)
plot(Lam,I2,'r','linewidth',1)
xlabel('Wavenumber','fontsize',14)
ylabel('Spectral Irradiance [W m^{-2} sr^{-1} nmm^{-1}]','fontsize',14)
%fh = figure(1);
%set(fh, 'color', 'white');
##### 2 CommentsShowHide 1 older comment
Torsten on 19 Sep 2022
Edited: Torsten on 19 Sep 2022
Your's is not quite correct.
It's not my result, it's yours. The formulae for I300 and I2 you use seem to be wrong.