Hey! Can someone help me calculate the binding energy of an exciton? I have been told to use the Rydberg energy but isn't the Rydberg energy derived using the kinetic energy of an atom in a circular orbit about a positve core (hydrogen atom), and the coulomb potential between the two? In an exciton there is no circular orbit, so how can the Rydberg energy be valid in this case?? Thanks for reading!