Gustav Kirchhoff
Gustav Robert Kirchhoff (
March 12,
1824 -
October 17,
1887),
physicist who is well known for his
electrical rules, Kirchhoff's voltage law and Kirchhoff's current law, which are fundamental to
circuit analysis in
electrical engineering. He was born in
Königsberg,
Prussia (now Kaliningrad,
Russia) and died in
Berlin, Germany.
In his spectroscopic collaboration with Bunsen, he was a co-discoverer of caesium and rubidium.
Kirchhoff's Law of Radiation
Kirchhoff formulated the following law in 1859, followed by a proof in 1861.
- The rate of emission of energy by a body is equal to the rate at which the body absorbs energy (both emission and absorption being in a given direction at a given wavelength).
In
1862 he introduced the term
black body radiation. Later, he produced three empirical laws describing the
spectral composition of
light emitted by incandescent objects.
Kirchhoff's Radiation Laws
- A hot solid object produces light with a continuous spectrum.
- A hot tenuous gas produces light with spectral lines at discrete wavelengths (i.e. specific colors) which depend on the energy levels of the atoms in the gas.
- A hot solid object surrounded by a cool tenuous gas (i.e. cooler than the hot object) produces light with an almost continuous spectrum which has gaps at discrete wavelengths depending on the energy levels of the atoms in the gas.
Reference