Figure 14.3-1

>  restart;
In this problem, we are going to generate figure 14.3-1
>  qble:=(lambda,T)->2*Pi*c^2*h/(lambda^5*(exp(c*h/
(lambda*kappa*T))-1)); 14.3-7
>  kappa:=1.3805e-16*erg/K; h:=6.624e-27*erg*s; 
c:=2.99793e10*cm/s;
>  qble(lambda,T);
>  evalf(qble(2e-4*cm,2000*K));
>  unit:=erg/(cm^3*s);
>  evalf(qble(2e-4*cm,2000*K)/unit); We need to do this since 
plot wants to give blanks if the units are left in place.
>  plot({qble(lam*1e-4*cm,2038*K)/unit,qble(lam*1e-4*cm,1538*K)
/unit,qble(lam*1e-4*cm,1204*K)/unit},lam=5e-2...10,
title=`Planck Dist. at 3700, 2800 and 2200F`, 
xtickmarks=10,color=[red,green,blue]);  plot of qble at three 
temperatures, note that the temperatures have been converted from 
F to K

We can also compute the integration at a constant T numerically 
without changing the variable of integration.
>  qbe1000:=evalf(int(qble(lambda*cm,1000*K),
lambda=0...infinity)); 

>  qbe1:=evalf(int(qble(lambda*cm,1*K),
lambda=0...infinity));