Background
John Kerr was born on December 17, 1824, in Ardrossan, Ayrshire, Scotland. He was the second son of Thomas Kerr, a fish dealer.
1860
John Kerr c. 1860, photograph by Thomas Annan.
1890
Royal Society, London, England
Kerr was elected to the Royal Society in 1890.
University of Glasgow, Glasgow, Scotland
Kerr attended the University of Glasgow, beginning in 1841, and received his Master of Arts degree with “highest distinction in Physical Science” in 1846.
John Kerr was born on December 17, 1824, in Ardrossan, Ayrshire, Scotland. He was the second son of Thomas Kerr, a fish dealer.
Kerr received part of his early education at a village school on Skye. He attended the University of Glasgow, beginning in 1841, and received his Master of Arts degree with “highest distinction in Physical Science” in 1846. He studied natural philosophy under David Thomson in 1845-1846 and then under William Thomson. Kerr was a member of the first group to work with William Thomson in the laboratory that was converted from a wine cellar and was known among the students as the “coal-hole.”
A divinity student, Kerr completed the courses in theology at the Free Church College in Glasgow but did not take up clerical duties.
In 1857 Kerr was appointed lecturer in mathematics at the Free Church Normal Training College for Teachers in Glasgow, remaining in this post for forty-four years. The facilities for research at this institution were limited, as was the time that Kerr could devote to it. Therefore the paucity of his publications is not surprising; their quality, however, is high.
Kerr is remembered primarily for two discoveries. The first, which he announced in 1875, was the birefringence developed in glass in an intense electric field. He bored holes into the ends of a piece of glass two inches thick until they were about a quarter of an inch apart. An intense electric field was applied to electrodes placed in these holes. The effect on a beam of polarized light shining perpendicular to the electric field was to give it elliptical polarization. The effect was strongest when the plane of polarization was at an angle of 45° to the field and zero when it was parallel or perpendicular to the field. In subsequent papers Kerr extended his findings to other materials, including a large number of organic liquids. He also found that the size of the effect was proportional to the square of the electric force.
Kerr’s second discovery, which bears his name, was announced at the meeting of the British Association in Glasgow in 1876, and an account was published the following year. The Kerr effect is detected when a beam of plane polarized light is reflected from the pole of an electromagnet. When the magnet is activated, the beam becomes elliptically polarized, with the major axis rotated from the direction of the original plane. Extended by Kerr and others, these experiments were first treated theoretically by George F. Fitzgerald in “On the Electromagnetic Theory of the Reflection and Refraction of Light” and in more general terms by Joseph Larmor in “The Action of Magnetism on Light.”
Kerr was elected to the Royal Society in 1890.
Kerr was married to Marion Balfour, and had three sons and four daughters.