Étienne-Louis Malus

Étienne-Louis Malus (1775 to 1812) was a French officer, engineer, physicist and mathematician. Born in Paris, he studied at a military engineering school where Gaspard Monge was among his teachers, and he took part in Napoleon's expedition to Egypt from 1798 to 1801 as a member of the mathematics section of the Institut d'Égypte. His mathematical work was almost entirely concerned with light. He studied geometric ray systems, which are closely connected to Julius Plücker's line geometry, and he rewrote Christiaan Huygens's theory of light in analytical form. He published his discovery of the polarization of light by reflection in 1809 and his theory of double refraction of light in crystals in 1810. He is best remembered for Malus's law, which gives the intensity of light that passes through a polariser placed in the path of an incident beam. He became a member of the Académie des Sciences in 1810, received the Royal Society's Rumford Medal in the same year, and died of tuberculosis in Paris at the age of 36.