Friedrich Carl Alwin Pockels
Encyclopedia
Friedrich Carl Alwin Pockels (1865–1913) was a German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 physicist. He was born in Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

 to Captain Theodore Pockels and Alwine Becker. He obtained a doctorate from the University of Göttingen in 1888, and from 1900 to 1913 he was professor
Professor
A professor is a scholarly teacher; the precise meaning of the term varies by country. Literally, professor derives from Latin as a "person who professes" being usually an expert in arts or sciences; a teacher of high rank...

 of theoretical physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

 at the University of Heidelberg.

In 1893 he discovered that a steady electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...

 applied to certain birefringent
Birefringence
Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...

 materials causes the refractive index
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....

 to vary, approximately in proportion to the strength of the field. The coefficient of proportionality is of the order of to . This phenomenon is now called the Pockels effect
Pockels effect
The Pockels effect , or Pockels electro-optic effect, produces birefringence in an optical medium induced by a constant or varying electric field. It is distinguished from the Kerr effect by the fact that the birefringence is proportional to the electric field, whereas in the Kerr effect it is...

.

His sister Agnes Pockels
Agnes Pockels
Agnes Luise Wilhelmine Pockels , was a German pioneer in chemistry.-Biography:In 1862, she was born in Venice, Italy. Her father served in the Austrian army. When he fell sick with malaria, the family moved to Brunswick, Lower Saxony in 1871. Already as a child, Agnes was interested in science and...

(1862-1935) was also a physicist.
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