John Kerr (1824 – 1907) Ardrossan-born physicist and pioneer in the field of electro-optics. The ‘Kerr-effect’ is named after him.

John Kerr was born on the 17th of December, 1824 in Ardrossan. The 4th child of Mary Miller and Thomas Kerr, the family reportedly lived on Princes Street before moving to Skye. It was here that John received some of his education in the parish school before attending Glasgow University. 

In 1846 he took classes with Professor William Thomson, later known as Lord Kelvin. Kerr was one of the first students to take Professor Thomson’s advanced class in mathematical physics and work in his new physical laboratory. He graduated M.A. with honours in 1849, distinguishing himself in maths and natural philosophy. That same year he went to Edinburgh where he studied at the Theological College of the Free Church of Scotland where he became an ordained minister. 

In September 1849 he married Marion Balfour from the Parish of Reay in Caithness. Their marriage lasted for over 40 years until her death in 1891. 

From 1857 to 1901 John taught mathematics at the Free Church Normal Seminary in Glasgow which became the Free Church Training College in 1900. It was during this time that Kerr discovered the double refraction of light in solid and liquid dielectrics in an electrostatic field, known as the ‘Kerr Effect’, also called the quadratic electro-optic (QEO) effect. The following year he discovered that light reflected from a magnetized material has a slightly rotated plane of polarization. His work was used in early television apparatus as a means of modulating beams of light. The ‘Kerr Effect’ has also been applied to digital photography to create a type of shutter with very short exposures and rapid reaction. 

He was awarded the honorary degree of LL. D. (Legum Doctor – Latin: “Teacher of Laws”) by Glasgow University in 1868 and elected a fellow of the Royal Society in 1890, receiving the society’s royal medal in 1898. 

Kerr was also an early champion of the metric system in the UK. Some of his early experiments, now known as “Kerr Cells” are preserved in Glasgow’s Hunterian Museum. 

He retired from teaching in 1901 and died on 15th August 1907 at his home in La Crosse Terrace, Glasgow aged 82 years old. 

Further Reading

Kerr Effect – Wikipedia