Friday, 18 October 2013

On This Day in Science History - October 17 - Kirchhoff Spectroscopy Laws

October 17th marks the passing of Gustov Kirchhoff. Kirchhoff was a German physicist who outlined basic laws of electronic circuits and blackbody radiation, but he is also known for his work in spectroscopy.

Kirchhoff formulated three laws to describe the individual spectral bands that are observed when looking through a prism at a hot gas. The first law says a hot, solid object will produce light in a continuous spectrum. The second law states that a hot gas will produce light of discrete wavelengths which are unique to the gas. The third law describes the opposite effect where a hot object surrounded by a cool gas produces light in a continuous spectrum, but with distinct wavelengths missing that are unique to the gas. Since these spectral bands are unique to each element, identifying the elements in a gas is like identifying people by fingerprints. This made identifying or discovering elements a lot easier than before.

Kirchhoff and Robert Bunsen used this technique to discover cesium and rubidium. His three spectral laws were a step towards a new branch of science that would become quantum mechanics. Find out what else occurred on this day in science history.


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