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
The Sound of a Flower The Sound of a Flower The Sound of a Flower () is 2015 South Korean period drama film based on the life of Jin Chae-seon, who became Joseon's first female "pansori" singer in 1867. Jin risks her life by cross-dressing as a man, at a time when women were forbidden to sing in public or perform on stage. The film focuses on the relationship between Jin and her pansori teacher, Shin Jae-hyo. The Korean title, "Dorihwaga", is a song written by Shin about his protégée after she became a court singer. The film was directed by Lee Jong-pil, who also