A) Show that the surface temperature of a star can be inferred from measurements of blackbodyfluxes at two different frequencies, even if the stellar radius and distance are unknown. b) Explain why in practice this method does not work well if both frequencies are on theRayleigh-Jeans side of the spectrum, hνkT.
c) Derive a simple, approximate expression for the temperature when both measurements areon the Wien tail, hνkT.
d) Derive an expression for the star’s radius if a distance measurement is also available (e. g.,from parallax).