"Planck's law" rho = 2 h nu^3 / c^2 / (exp(h nu / k / T) - 1) rho "For T = 3000 kelvin" T = 3000 kelvin c = 299792458 meter / second h = 6.62607015 10^(-34) joule second -- exact since 2019 definition of kilogram k = 1.38064852 10^(-23) joule / kelvin rho = eval(rho, nu, nu / second) meter^2 / joule -- cancel physical units rho "Radiant energy (rho) vs frequency (nu)" xrange = (0,10^15) yrange = (0,10^(-8)) draw(rho,nu)