Henri Becquerel received one half of the 1903 Nobel Prize in Physics.
The Swedish Academy awarded the other half jointly to Marie Curie and Pierre Curie, so each Curie received one quarter. Becquerel was honored for discovering spontaneous radioactivity, while the Curies were recognized for their joint investigations of the radiation he had found.
Becquerel’s discovery began in 1896, shortly after Wilhelm Röntgen announced X-rays. Becquerel investigated whether phosphorescent uranium compounds might emit similar rays after exposure to sunlight. A chance interruption caused him to leave uranium salts near wrapped photographic plates, which later showed signs of exposure even without sunlight. He concluded that uranium emitted penetrating radiation spontaneously.
The prize’s division is easy to misremember because three scientists shared the award. It was not divided equally among three people: Becquerel received one-half, and Marie and Pierre Curie divided the remaining half. The award recognized related but distinct contributions—Becquerel’s initial discovery and the Curies’ extensive study of the phenomenon and radioactive elements.