Doctor John Kerr, Scottish mathematician and physicist, c 1870.
© Science Museum / Science & Society Picture Library
Doctor John Kerr (1824-1907) studied at Glasgow University where he became a research student of Lord Kelvin. In 1876 Kerr discovered the magneto-optic effect which bears his name. He was elected to the Royal Society in 1890 and was awarded a Royal Medal in 1898.