Either include all of them as arguments:
R=@(wl,T,h,c,k) 2*pi*c^2*h./(wl.^5)./(exp(h*c./wl/k/T)-1);
h=6.626e-34;
c=3e8;
k=1.38e-23;
wl=1E-9:0.1:3;
T = 273;
figure
plot(wl,R(wl,T,h,c,k) )
grid
or define the ‘R’ function after assigning the constants:
%Black body radiation graph
h=6.626e-34;
c=3e8;
k=1.38e-23;
R=@(wl,T) 2*pi*c^2*h./(wl.^5)./(exp(h*c./wl/k/T)-1);
wl=1E-9:0.1:3;
T = 273;
figure
plot(wl,R(wl,T))
grid
Regardless, the constants must exist in your workspace before the ‘R’ function is called.
Both of these will work.
