the formula in question in part a) to do with the energy density per unit volume in the frequency range ν to ν+dv for black-body radiation at a temperature of T.
(a) Rewrite this equation in terms of the wavelength interval λ to λ+dλ. (Note that you'll need to take into account the difference between the size of an element of wavelength and an element of frequency). (b) Find an expression for the wavelength at which the expression in part
(a) has its peak. Estimate the temperature of the surface of the Sun, given that the peak of its spectrum is at 4800 A˚.
(c) If the spectrum of another star peaks at 3000 A˚, and the luminosity of this star is 100 times fainter than the Sun, what is this star's radius (in solar radii)?