How did Becquerel discover radioactivity?
The discovery was a result of patient observation and systematic experimentation. Following Henri Hertz's work on cathode rays, I was investigating the relationship between phosphorescence and x-rays. I exposed uranium salts to sunlight, as was common in phosphorescence studies, and then placed them on photographic plates wrapped in black paper. Upon developing the plates, I found they were fogged, suggesting rays had passed through the paper. This appeared to be linked to the phosphorescence of the uranium salts. However, further investigation revealed that the effect persisted even when the salts were kept in darkness, indicating an independent emission of these rays, which I detailed in 'Sur la phosphorescence des sels d'uranium.'
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