Radiation-pressure forces exerted on an absorbing body in a dielectric fluid

The reaction force exerted on the matching unit required to isolate a source from a dielectric fluid containing an absorbing body is considered. In this way, it is shown that a substitution of ¿g = c in the general radiation-pressure result P¿g/c2 is only permissible for the particular cases of a perfect match, or when the dielectric fluid is extended to enclose the source.