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 A Web of Sound A Web of Sound is the second album by the American garage rock band the Seeds. Produced by Marcus Tybalt and released in October 1966, it contained the single "Mr. Farmer" and the 14-minute closing song "Up In Her Room". The album did not chart, though it has received generally favorable reviews from music critics. Lead singer Sky Saxon conceptualized the album's cover design depicting the four Seeds members trapped in a spider's web. "A Web of Sound" was produced by Saxon under the pseudonym Marcus Tybalt; Saxon also wrote or co-wrote all of the songs