Does the impedance of an RL series circuit varies inversely with the frequency?

The simple answer is no. The impedance of an R-Lcircuit is the vector sum of the circuit's resistance and its inductive reactance. Resistance is determined by the length, cross-sectional area, and resistivity of the conductor (although its 'a.c. resistance' is proportional to the frequency squared), whereas the inductive reactance is directly proportional to the frequency of the supply.