ploting planck's function

[Alexandre Abbes]

Hello,

I teach mathematics in a lycée, and I would like to use scilab to plot 
curves.

I was trying to plot the planck's law function, but I do not have the 
expected curve, this might be due to precision problems.

We have f(l)=(2hc^2/l^5)* 1/(exp(hc/(ktl))-1) 
(http://en.wikipedia.org/wiki/Planck%27s_law)

l is the wavelength.
T=1000 (temperature).

and c=3e8, k=1.3e-23, h=6.3e-34.

The curve I get is increasing, and looks like a parabola, wich is false, 
obviously. I get a better result with maxima, by the way.

Does anybody know how to increase the precision?

best regards

Alexandre Abbes
Mathématiques sections européennes
Lycée Marcelin Berthelot, Toulouse.