[SOLVED] radius of the fermi sphere 1. The problem statement, all variables and given/known data On page 249 of ISSP, Kittel says that the radius of a free electron Fermi sphere is [tex]k_F = \left(3 \pi^2 n \right)^{1/3}[/tex] where n is the concentration of electrons. I don't know why that is true. EDIT: never mind; they derive that on page 138 2. Relevant equations 3. The attempt at a solution