[2] Following suggestions by François Arago, Léon Foucault and Fizeau collaborated in a series of investigations on the interference of light and heat.

[4] In 1849, Fizeau calculated a value for the speed of light to a better precision than the previous value determined by Ole Rømer in 1676.

[7] In 1850 he measured the relative speeds of light in air and water, using a rotating mirror, however Foucault independently achieved the same result seven weeks earlier.

In 1853, Fizeau described the use of a capacitor (sometimes termed a "condenser") as a means to increase the efficiency of the induction coil.

Later, he studied the thermal expansion of solids and applied the phenomenon of interference of light to the measurement of the dilatations of crystals.