Abstract
The integrated density of states (IDS) of light is examined by introducing a pseudopotential for the scattering of transverse electromagnetic fields. The two formulas, electromagnetic versions of the well-known formulas of electrons, are given for the change of IDS due to spherical scatterers, the one for a single scatterer and the other for a periodic array of scatterers. It is shown that they are expressed in terms of the phase shifts of light and have the forms quite analogous to the electronic counterparts except that the number of the phase shifts is doubled due to the transversality of electromagnetic fields.