Étienne Louis Malus (23.07.1775-24.02.1812) was a French physicist and a member of the Paris Academy of Sciences (1810). He was born in Paris. He graduated from the École Polytechnique (1796) and served in the engineering corps. From 1808 he lived in Paris and worked at the École Polytechnique.
His work concerned optics. In 1808 he discovered the polarisation of light on reflection and established the law of the change in intensity of polarised light (Malus's law). He developed a theory of the double refraction of light in crystals. In 1811, independently of J. Biot, he detected the polarisation of light on refraction. He proposed (1811) a method of determining the optical axis of a crystal. He designed a number of polarisation instruments.
The B. Rumford Medal (1811).