In Chapter 22 we saw that the Debye temperature for a solid is typically several hundred kelvins. There are as many phonon states as there are atoms in the solid. Suppose that, for a certain solid at 100 K, the occupation number for a particular phonon state is 1/2.
(a) Roughly what is the occupation number of this state at 0.1 K?
(b) Repeat the above for a state whose occupation number is 1/2 at 5 K.