John Kerr (physicist)
|John Kerr (physicist)|
John Kerr, c. 1860, photograph by Thomas Annan
17 December 1824|
|Died||15 August 1907
|Known for||Kerr effect|
Life and work
John Kerr was born on 17 December 1824 at Ardrossan, Scotland. He was a student in Glasgow from 1841 to 1846, and at the Theological College of the Free Church of Scotland, in Edinburgh, in 1849. Starting in 1857 he was mathematical lecturer at the Free Church Training College in Glasgow. He died in Glasgow in 1907.
Kerr's most important experimental work was the discovery of double refraction in solid and liquid dielectrics in an electrostatic field (1875) and of the so-called Kerr effect. In the Kerr effect, a 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 phenomenon for magnetic fields, and it is now called 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.
The Kerr 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 to measure its speed. Earlier measurements had used mechanical means of modulation achieving frequencies of around 10 kHz, but the Kerr cell allow frequencies of 10 MHz and greater precision of measurement. Kerr's original cell was a glass block. Modern cells are more commonly filled with liquids such as nitrobenzene.
- Honorary LL.D from the University of Glasgow (1864)
- Fellow of the Royal Society (1890)
- Royal Medal of the Royal Society (1898)
- Civil list pension (1902)
- Steele (2004)
- See the very brief biographical sketch in Lewis, E. P. (Editor), The Effects of a Magnetic Field on Radiation (1900), New York: American Book Company, page 64
- See Kerr, J. (1863) The Metric System, Its Prospects in this Country, Effingham Wilson (publisher)
- Gray, Robert C. (17 August 1935). "The Rev. John Kerr, F.R.S., Inventor of the Kerr Cell". Nature 136 (3433): 245–247. Bibcode:1935Natur.136..245G. doi:10.1038/136245a0.
- Green, G.; Lloyd, J. T. (1970). Kelvin's Instruments and the Kelvin Museum. Glasgow: University of Glasgow. pp. 55–56. ISBN 0-85261-016-5.
- See also Green, George (March 1972). "Kelvin's Instruments and the Kelvin Museum". American Journal of Physics 40 (3): 496–497. Bibcode:1972AmJPh..40..496G. doi:10.1119/1.1986598.
- Kerr, John (1867) An Elementary Treatise on Rational Mechanics, William Hamilton (publisher)
- Steele, R. rev. Anita McConnell (2004) "Kerr, John (1824-1907)", Oxford Dictionary of National Biography, Oxford University Press, accessed 19 June 2005 (subscription or UK public library membership required)
- Weinberger, P. (2008). "John Kerr and his Effects Found in 1877 and 1878" (PDF). Philosophical Magazine Letters 88 (12): 897–907. Bibcode:2008PMagL..88..897W. doi:10.1080/09500830802526604.