This problem deals with blackbody radiation. (spec- tral) emissivity in some texts referred to as irradiance) of a body at a given wavelength expresses the emitted energy per unit surface in unit time per unit wavelength. total emissivity expresses the total (wavelength-integrated) emit- ted energy in unit time per unit surface. derive the expression for the ratio of spectral emissivities of two black- bodies of temperatures ti and t2. (4 points) derive the expression for the ratio of total emissivities of two blackbodies of temperatures t1 and t2. (4 points) assuming that they radiate as blackbodies, compare the ratio of spectral emissivities at 500 nm to the ratio of total emissivities for a human body ( t 300 k) and tungsten filament (2500 k). (4 points) now, compare the total emitted power of a human body and a tungsten filament. (estimate the quantities that are missing, if any, using your best judgment). (4 points) the earth receives total of 1400 w/m2 from the sun. if the illuminated surface would emit as a blackbody, what would be its temperature? in which part of the spectrum would the maximum emission of that surface be? (4 points)