For the thermal radiation from an ideal blackbody radiator witha surface temperature of 2100 K, let Ic represent the intensity perunit wavelength according to the classical expression for thespectral radiancy and Ip represent the corresponding intensity perunit wavelength according to the Planck expression. What is theratio Ic/Ip for a wavelength of (a) 400 nm (at the blue end of thevisible spectrum) and (b) 210 μm (in the far infrared)? (c) Doesthe classical expression agree with the Planck expression in theshorter wavelength range or the longer wavelength range?
