Photochemistry



 Photochemistry, a sub-discipline of electromagnetic radiation).[1]

Like most scientific disciplines, photochemistry utilizes the SI or metric measurement system. Important units and constants that show up regularly include the physical chemistry.

The first law of photochemistry, known as the Grotthuss-Draper law (for chemists Theodor Grotthuss and photochemical reaction to take place.

The second law of photochemistry, the Stark-Einstein law, states that for each photon of light absorbed by a chemical system, only one molecule is activated for a photochemical reaction. This is also known as the photoequivalence law and was derived by Albert Einstein at the time when the quantum (photon) theory of light was being developed.

Photochemistry may also be introduced to laymen as a reaction that proceeds with the absorption of light. Normally a reaction (not just a photochemical reaction) occurs when a molecule gains the necessary activation energy.

The absorption of a photon of light by a reactant molecule may also permit a reaction to occur not just by bringing the molecule to the necessary activation energy, but also by changing the symmetry of the molecule's electronic configuration, enabling an otherwise inaccessible reaction path, as described by the pericyclic reaction that can be analyzed using these rules or by the related frontier molecular orbital theory.

Main concepts

The pillars of photochemistry are photosynthesis in biochemistry.

Regions of the electromagnetic spectrum

The electromagnetic spectrum is broad, however, a photochemist will find themselves working with several key regions. Some of the most widely used sections of the electromagnetic spectrum include:

  • Visible Light: 400–700 nm wavelengths
  • Ultraviolet: 100–400 nm wavelengths
  • Near Infrared: 700–1000 nm wavelengths
  • Far infrared: 15–1000 µm wavelengths

Applications

There are important processes based in the photochemistry principles. One case is Adenosine Triphosphate. Medicine bottles are made with darkened glass to prevent the medicine itself from reacting chemically with light. In fireflies, an odorant) to otherwise odorless natural gas.

See also

References

  1. ^ International Union of Pure and Applied Chemistry. "photochemistry". Compendium of Chemical Terminology Internet edition.
 
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