Well, I doubt they're tough, but I have no idea what's even being asked, or how I should go about solving these things. The questions are: Use the bBohr quantization rules to caluclate the energy levels for a harmonic oscillator, for which the energy is p²/2m + mw²r²/2; that is, the force is mw²/r. Restrict yourself to circular orbits. What is the analog of the Rydberg formula? Show that the correspondence principle is staisfied for all values of the quantum number n used in quantizing the angular momentum. Any general clarifications as to what is even being asked would be helpful. The second question is: The classical energy of a plane rotator is given by E = L²/2I where L is the angular momentum and I is the moment of inertia. Apply the Bohr quantization rules to obtain the energy levls of the rotator. If the Bohr frequency condition is assumed for the radiation in transitions from states labeled by n1 to states labled by n2, show that (a) the correspondence principle holds, and (b) that it implies that only transitions Delta-n = +/- 1 should occur.