Abstract: Surface modes at the interface of two isotropic mediums are investigated and the law of Brewster is analyzed in another aspect.When the incident lights match the surface modes at the interface,the energy of incident lights will transfer to the eigen states at the interface.If the electromagnetic fields in the refractive medium have propagating modes,the surface modes will generate new propagating electromagnetic waves in the refractive medium,forming transmission waves with all the energy of incident lights.This phenomenon of total transmission has been described by the Brewster law,and this can also be viewed as a behavior of optical resonance.The total transmission of transverse magnetic or transverse electric fields is always observed at the interface of two isotropic mediums with the same permeability or permittivity.

Key words: surface modes, Brewster’s law, optical resonance