Kirchhoff's law of thermal radiation rarefied material such as air, or transparent material, through which observations can be made. The interface is not a material body and can neither emit nor absorb. It is a mathematical surface belonging jointly to the two media that touch it. It is the site of refraction of radiation that penetrates it and of reflection of radiation that does not. As such it obeys the Helmholtz reciprocity principle. The opaque body is considered to have a material interior that absorbs all and scatters or transmits none of the radiation that reaches it through refraction at the interface. In this sense
A Web of Sound listening to them is humming in a room where another dozen people are humming also, in a constant pitch, never varying, unchanging." Allmusic's Joe Viglione suggested that "A Web of Sound" also influenced such artists as Iggy Pop and The Stooges and Alice Cooper. Stewart Mason, also of Allmusic, remarked that the album blended "the snotty aggression of ["The Seeds"] a bit with some heavier psychedelic flourishes." Writer Malcolm Russell described "A Web of Sound" as being "more adventurous" than the band's debut album, and said it "brimmed with scratchy mid-60s classics." Don Jacobson of "The Beachwood Reporter" called it