HOMEWORK 1 Stellar Astrophysics 1a. How much more energy is emitted by a star at 20,000 K than one at 5,000 K? (Assume the sizes are similar.) 1b. What is the predominate color of each star in part (a)? Use Wien’s Law and express your answers in nm. 2a. What is the energy of one photon of wavelength != 300 nm? Express your answer both in joules and in electron volts. 2b. An atom in the second excited state (n = 3) of hydrogen is just barely ionized when a photon strikes the atom.