The exiton is a hydrogen atom-like entity encountered in advanced semiconductor work. It consists of an electron bound to a +q charged particle (a hole) of approximately equal mass. Bohr atom results can be used in computing the allowed energy states of the exciton provided the reduced mass, m_r=m_+ m_-/(m_++m_-)m_0/2, replaces the electron mass in the Bohr atom formulation. In addition, the distance between the components of the exciton is always such that there are intervening semiconductor atoms. Thus e in the Bohr formulation must also be replaced by Ks e0, where Ksis the semiconductor dielectric constant. Using Ks = 11.8, determine the ground state (n = 1) energy of an exciton in Si.