Rev. John Kerr (December 17, 1824 – August 15, 1907) was a Scottish physicist who inaugurated the field of electro-optics. December 17 is the 351st day of the year (352nd in leap years) in the Gregorian Calendar. ... 1824 was a leap year starting on Thursday (see link for calendar). ... August 15 is the 227th day of the year in the Gregorian Calendar (228th in leap years), with 138 days remaining. ... 1907 (MCMVII) was a common year starting on Tuesday (see link for calendar) of the Gregorian calendar (or a common year starting on Wednesday of the 13-day-slower Julian calendar). ... Motto: (Eng: No one provokes me with impunity)1 Anthem: Multiple unofficial anthems Capital Edinburgh Largest city Glasgow Official language(s) English, Gaelic, Scots 2 Government Constitutional monarchy  - Queen of the UK Queen Elizabeth II  - Prime Minister of the UK Tony Blair MP  - First Minister Jack McConnell MSP Unification    - by... Physicists working in a government lab A physicist is a scientist who studies or practices physics. ... Electro-optics is a branch of technology involving components, devices and systems which operate by modification of the optical properties of a material by an electric field. ...

Life

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. Ardrossan is a town located on the North Ayrshire coast in western Scotland. ... The Guppy (Poecilia reticulata) is one of the most popular freshwater aquarium fish species in the world. ... Merchants function as professionals who deal with trade, dealing in commodities that they do not produce themselves, in order to produce profit. ... The University of Glasgow was founded in 1451, in Glasgow, Scotland. ... Theology (Greek θεος, theos, God, + λογος, logos, word or reason) means reasoned discourse concerning religion, spirituality and God. ... This article concerns the Free Church of Scotland 1843-1900, for the Free Church of Scotland existing from 1900 to the present day see Free Church of Scotland (post 1900). ... Euclid, Greek mathematician, 3rd century BC, known today as the father of geometry; shown here in a detail of The School of Athens by Raphael. ... Physics (from the Greek, (phúsis), nature and (phusiké), knowledge of nature) is the science concerned with the discovery and understanding of the fundamental laws which govern matter, energy, space and time. ... William Thomson, Archbishop of York, has the same name as this man. ... Natural philosophy or the philosophy of nature, known in Latin as philosophia naturalis, is a term applied to the objective study of nature and the physical universe that was regnant before the development of modern science. ... 1846 was a common year starting on Thursday (see link for calendar). ...

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. 1857 was a common year starting on Thursday (see link for calendar). ... The Free Church Training College was established by the Free Church of Scotland in 1845 as a college for teacher training. ... For other uses, see Glasgow (disambiguation). ... 1875 (MDCCCLXXV) was a common year starting on Friday (see link for calendar). ... The Kerr effect or the quadratic electro-optic effect is a change in the refractive index of a material in response to the intensity of an external electric field. ... Electric potential is the potential energy per unit of charge associated with a static (time-invariant) electric field, also called the electrostatic potential, typically measured in volts. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific context, electromagnetic radiation of any wavelength [citation needed]. The elementary particle that defines light is the photon. ... The refractive index (or index of refraction) of a material is the factor by which the phase velocity of electromagnetic radiation is slowed in that material, relative to its velocity in a vacuum. ... This article treats polarization in electrodynamics. ... A calcite crystal laid upon a paper with some letters showing the double refraction Birefringence, or double refraction, is the decomposition of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals, depending on... This article treats polarization in electrodynamics. ...

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 photography, a shutter is a device that administers the exposure by admitting light to the film for a specific period of time. ... Photography is the process of making pictures by means of the action of light. ... 1928 (MCMXXVIII) was a leap year starting on Sunday (link will take you to calendar). ... Modulation is the process of varying a carrier signal, typically a sinusoidal signal, in order to use that signal to convey information. ... The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning swiftness. It is the speed of all electromagnetic radiation in a vacuum, not just visible light. ... Modulation is the process of varying a carrier signal, typically a sinusoidal signal, in order to use that signal to convey information. ... Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... A kilohertz (kHz) is a unit of frequency equal to 1,000 hertz (1,000 cycles per second). ... MegaHertz (MHz) is the name given to one million (106) Hertz, a measure of frequency. ... Glass can be made transparent and flat, or into other shapes and colors as shown in this sphere from the Verrerie of Brehat in Brittany. ... A liquid will usually assume the shape of its container. ... Chemical structure of nitrobenzene Nitrobenzene, also known as nitrobenzol or oil of mirbane, is a poisonous organic compound with an almond odor and chemical formula C6H5NO2. ...

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. The Kerr effect or the quadratic electro-optic effect is a change in the refractive index of a material in response to the intensity of an external electric field. ... The refractive index (or index of refraction) of a material is the factor by which the phase velocity of electromagnetic radiation is slowed in that material, relative to its velocity in a vacuum. ... In physics, an electric field or E-field is an effect produced by an electric charge (or a time-varying magnetic field) that exerts a force on charged objects in the field. ... The Pockels effect, or Pockels electro-optic effect, is the production of birefringence in an optical medium induced by a constant or varying electric field. ... To meet Wikipedias quality standards, this article may require cleanup. ... Magneto-optic Kerr effect (MOKE) is one of the magneto-optic effects. ... // Experiment using a (likely argon) laser. ...

Kerr was an early champion of the metric system in the UK. The International System of Units (symbol: SI) (for the French phrase Syst me International dUnit s) is the most widely used system of units. ...

He died in Glasgow. For other uses, see Glasgow (disambiguation). ...

Honours

• 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)

Legum Doctor (English: Doctor of Laws; abbreviated to LL.D.) In the UK the LL.D. is a higher doctorate awarded on the basis of exceptionally insightful and distinctive publications, containing significant and original contributions to the science or study of law. ... The University of Glasgow was founded in 1451, in Glasgow, Scotland. ... 1864 (MDCCCLXIV) was a leap year starting on Friday (see link for calendar) of the Gregorian calendar or a leap year starting on Sunday of the 12-day-slower Julian calendar. ... The premises of the Royal Society in London (first four properties only). ... 1890 (MDCCCXC) was a common year starting on Wednesday (see link for calendar) of the Gregorian calendar (or a common year starting on Friday of the Julian calendar). ... The Royal Medals of the Royal Society of London were established by King George IV. They were further supported with certain changes to their conditions, by King William IV and Queen Victoria. ... 1898 (MDCCCXCVIII) was a common year starting on Saturday (see link for calendar) of the Gregorian calendar (or a common year starting on Monday of the 12-day-slower Julian calendar). ... A civil list is a list of individuals to whom money is paid by the government. ... The examples and perspective in this article or section may not represent a worldwide view. ... 1902 (MCMII) was a common year starting on Wednesday (see link for calendar). ...

Bibliography

Works by Kerr

• The Metric System (1863)
• An Elementary Treatise on Rational Mechanics (1867)

1863 (MDCCCLXIII) is a common year starting on Thursday of the Gregorian calendar (or a common year starting on Saturday of the Julian calendar). ... 1867 (MDCCCLXVII) was a common year starting on Tuesday (see link for calendar). ...

About Kerr

• Obituaries:
  • The Times, August 19, 1907, 12c
  • Nature, 76 (1907), 575–6
• Green, G. & Lloyd, J.T. (1970) Kelvin's instruments and the Kelvin Museum pp55–6

The Times is a national newspaper published daily in the United Kingdom since 1785, and under its current name since 1788. ... First title page, November 4, 1869 Nature is one of the oldest and most reputable scientific journals, first published on 4 November 1869. ...

External links

• Steele, R. (2004) "Kerr, John (1824-1907)’, rev. Anita McConnell, Oxford Dictionary of National Biography, Oxford University Press, 2004 <http://www.oxforddnb.com/view/article/34300, accessed 19 June 2005> (subscription required)