The French physicist who independently discovered the Doppler effect for electromagnetic waves in 1848 was Hippolyte Fizeau.
Fizeau, whose full name was Armand Hippolyte Louis Fizeau, was born in Paris in 1819. He studied light, photography, interference, and the measurement of its speed. In 1848, he recognized that motion should shift the frequency of electromagnetic waves, including light. This was independent of Christian Doppler’s 1842 proposal, which had focused on wave frequency and the apparent colors of stars.
The result is often called the Doppler–Fizeau effect in French-speaking contexts. Fizeau’s work helped connect Doppler’s general wave principle with optical astronomy, where shifts toward longer wavelengths indicate recession and shifts toward shorter wavelengths indicate approach. Astronomers now use these changes to measure stellar and galactic radial velocities.
Fizeau is also remembered for measuring the speed of light with a toothed rotating wheel in 1849 and for his 1851 experiment involving light traveling through moving water. A common confusion is Léon Foucault, who also made major optical discoveries and independently measured light’s speed in water, but was not the physicist credited with the 1848 electromagnetic Doppler discovery.