//Example 16.1//

l=400*10^-9;//m //meter //wavelength
h=(0.6626*10^-33);//J s //Joule-second //Plank's constant
a=0.2998*10^9;//m/s //speed of light
c=(6.242*10^18);//eV/J //1 Coulomb of charge
E=((h*a)/l)*c
mprintf("E = %f eV",E)