1. Show that the quantization of angular momentum L = n U follows from Bohr's Assumption D that the mean value K of the kinetic energy of the electron- nucleus system is given by K = nhforb/2. Assume a circular orbit.
2. (a) Calculate the energies of the three lowest states of positronium.
(b) Determine the wavelengths of the Ka, K/3, La, and L/3 transitions.
3. Careful measurements of light from a distant galaxy show that the longest observed wavelength in the Lyman series of hydrogen is 137.15 nm. If the galaxy is moving directly away from us, what is its velocity?