A derivation of the energy densities and power flows of plasma waves in a planar two‐dimensional electron‐ion plasma is presented through a simple approach. In this method, the response of an external current density introduced into the system is determined by a so‐called dispersion function. The advantage of the dispersion function is that it yields not only the dispersion relations of both plasmon (high‐frequency) and ion‐acoustic (low‐frequency) waves of the system, but expressions for the energy relations as well.
