1. The problem statement, all variables and given/known data Show that in the Bohr model, the frequency of revolution of an electron in its nth In classical physics, the frequency of revolution of the electron is equal to the frequency of radiation it emits. Show that when n is very large, the frequency of revolution is equal to the frequency radiated upon transition of the electron from orbit (n+ 1) to n (Bohr’s correspondence principle).  Assume that a proton is orbiting a black hole under the sole inﬂuence of gravity. It produces an emission spectrum equivalent to that of a hydrogen atom, but with frequencies multiplied by a factor of 10−6 . Disregarding relativistic eﬀects, calculate the mass of the black hole which would explain the observed emission spectrum. Show that the radius of the proton’s orbit is proportional to the square of the quantum number n and ﬁnd the radius of the ﬁrst orbit. 2. Relevant equations 3. The attempt at a solution 1 equation, 2 unknowns. Not sure how to calculate mass of star in the first place..