Reciprocity of the impulse response for scattering from inhomogeneous media and arbitrary dielectric bodies

Using the angular-spectrum representation of wave fields, I have introduced the impulse responses for transmission and reflection of a scalar wave on interaction with an inhomogeneous layer or arbitrary dielectric body. Then, by using the S-matrix formalism within the framework of this angular spectrum representation, reciprocity relations for the impulse responses are obtained. The theory shows the lack of contribution of evanescent waves to these reciprocity relations.