Deriving Average Energy of an Oscillator: Thermal Radiation

[sai2020]

The question:

In 1900, Planck used an abstract model consisting of harmonic oscillators with various frequency. Derive an average energy $$\bar{\epsilon}$$ of a single oscillator where the oscillators of frequency f can only take on discrete energies $$\epsilon$$$$_{n}$$ = nhf, n=0, 1, 2, ... and the Boltzmann probability distribution, P($$\epsilon$$$$_{n}$$) = exp(-$$\epsilon$$$$_{n}$$ / k$$_{B}$$T). (Note: Boltzmann showed that the probability for a system at equilibrium to have an energy E is proportional to exp(-$$\epsilon$$$$_{n}$$ / k$$_{B}$$ T, where k$$_{B}$$ is the Boltzmann constant.

I have no idea what he is talking about and my textbook doesn't say anything either. Can someone point me to a good book about these stuff?

 

[mangoo87]

R. Eisberg, R. Resnick
Quantum physics of atoms, molecules, solids, nuclei and participles

 

[sai2020]

Thanks a lot. It's a beautiful book