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Kerr, John

optical effect free birefringence

(1824–1907) British physicist: discovered the electro-optical and magneto-optical Kerr effects.

Kerr was educated at the University of Glasgow, becoming a research student with Lord Kelvin , and working with him in the converted wine cellar known as ‘the coal hole’. He later became a lecturer in mathematics at the Free Church Training College for Teachers in Glasgow, continuing his research in his free time.

Kerr is best remembered for the effect that bears his name. In 1875 he showed that birefringence (double refraction) occurs in some materials such as glass when subjected to a high electric field. With great experimental skill he showed that the size of the effect is proportional to the square of the field strength; the electro-optical Kerr effect is used today as the basis for ultra-fast optical shutters ( c .10 –10 s), using a Kerr cell in which a liquid (eg nitrobenzene) undergoes birefringence. He also discovered the magneto-optical Kerr effect, in which plane-polarized light reflected from the polished pole of an electromagnet becomes elliptically polarized; the effect has been used in the study of domain structure and other magnetic properties of ferromagnetic materials.

Kessler-Harris, Alice (1941–) - U.S. Labor and Women’s History [next] [back] Kerger, Paula A. - President and Chief Executive Officer of Public Broadcasting Service, Career, Sidelights

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