John Kerr (physicist)

John Kerr (physicist)

Rev. John Kerr (December 17, 1824 – August 15,1907) was a Scottish physicist who inaugurated the field of electro-optics.


Born in Ardrossan to a fish merchant, Kerr attended the University of Glasgow from where he earned a master's degree in divinity, subsequently being ordained a minister of the Free Church of Scotland. He also displayed an enthusiasm and ability in mathematics and physics and when his contemporary Lord Kelvin became professor of natural philosophy in 1846 the two became close friends, Kerr helping Kelvin to found the first physical laboratory at a British university.Steele (2004)]

In 1857, Kerr became lecturer in mathematics and physical science at the Free Church Training College in Glasgow. It was there, in 1875, that he discovered the Kerr electro-optic effect. A strong electric potential, applied in a direction normal to a beam of light, causes a difference in refractive index for light polarised in the plane of the field and light polarised normal to it, an effect known as birefringence. This causes the resultant polarisation of the light to change.

The effect is exploited in the "Kerr cell" which is used in applications such as shutters in high-speed photography, with shutter-speeds as fast as 100 ns. In 1928 Karolus & Mittelstaedt used a Kerr cell to modulate a beam of light in order to measure its speed. Earlier measurements had used mechanical means of modulation achieving frequencies of around 10 kHz while the Kerr cell allow frequencies of 10 MHz and greater precision of measurement. Kerr's original cell was a glass block while modern cells are more commonly filled with liquids such as nitrobenzene.

In the Kerr Effect, the change in refractive index is proportional to the square of the electric field. Where the relationship is linear, the effect is known as the Pockels effect. Kerr also demonstrated a similar effect for magnetic fields known as the magneto-optic Kerr effect. Light from lasers allows the achievement of the effect using the light's own electric field, the "AC Kerr effect".

Kerr was an early champion of the metric system in the UK.

He died in Glasgow.


*Honorary LL.D from the University of Glasgow in recognition of his contributions to physical science (1864);
*Fellow of the Royal Society (1890);
*Royal Medal of the Royal Society (1898);
*Civil list pension (1902).



**"The Times", August 19, 1907, 12"c"
**"Nature", 76 (1907), 575–6----
*Green, G. & Lloyd, J.T. (1970) "Kelvin's instruments and the Kelvin Museum" "pp"55–6
*Kerr, K. (1863) "The Metric System"
*— (1867) "An Elementary Treatise on Rational Mechanics"
*Steele, R. rev. Anita McConnell (2004) " [ Kerr, John (1824-1907)] ", "Oxford Dictionary of National Biography", Oxford University Press, accessed 19 June 2005 ODNBsub

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • John Kerr — may refer to one of the following:Government and politics* John Kerr (Governor General) (1914 ndash;1991), Australian Governor General * John Kerr (US politician) ( c. 1778 ndash;1823), Irish born mayor of Columbus, Ohio * John Leeds Kerr (1780… …   Wikipedia

  • Frank John Kerr — (January 8, 1918 September 15, 2000) was an Australian astronomer and physicist who made contributions to human understanding of the galactic structure of the Milky Way. Born in St Albans to Australian parents, Kerr returned with his family to… …   Wikipedia

  • Kerr (surname) — For people with the given name, see Kerr (given name). For other uses, see Kerr. Kerr is a surname, traditionally pronounced either cur , care or carr . In Scotland, it is pronounced kehr with a trilled r and the vowel sounded as long eh as in… …   Wikipedia

  • Kerr cell — noun optical device consisting of a transparent cell with two electrodes between two polarizing media; passes light only if the two planes of polarization are parallel; used as a high speed shutter or to modulate a laser beam • Hypernyms:… …   Useful english dictionary

  • Kerr effect — This article is about the Kerr nonlinear optical effect. For the magneto optic phenomenon of the same name, see magneto optic Kerr effect. The Kerr effect, also called the quadratic electro optic effect (QEO effect), is a change in the refractive …   Wikipedia

  • Kerr electro-optic effect — ▪ physics       in physics, the inducement of double refraction of light in a transparent substance when a strong electric field is applied in a direction transverse to the beam of light. In double refraction, the index of refraction (a measure… …   Universalium

  • Kerr effect — /ˈkɜr əfɛkt/ (say kerr uhfekt) noun the rotation of the plane of polarisation of light when it is passed through certain liquids or solids to which an electric field is applied (electro optical effect), or to which a magnetic field is applied… …   Australian English dictionary

  • Kerr effect — Physics. the double refraction of light in certain substances, produced by an electric field. [1905 10; named after John Kerr (1824 1907), Scottish physicist] * * * …   Universalium

  • John B. McDiarmid — JOHN BRODIE MCDIARMID (June 6, 1913 April 15, 2002)John B. McDiarmid played an important role in Canadian Naval Intelligence during WWII. He was chairman of the Classics Department at the University of Washington and was the university’s first… …   Wikipedia

  • Kerr , John — (1824–1907) British physicist Born at Ardrossan in Scotland, Kerr studied at Glasgow University and carried out research work under Lord Kelvin. He taught mathematics at a training college in Glasgow. He is remembered for his work on polarized… …   Scientists