Radioactivity
Source: Always Images
One happy accident often leads to another. That was the case with French scientist Henri Becquerel, who, after being inspired by Röntgen’s work, started researching phosphorescence in 1896. Becquerel thought that phosphorescence was responsible for the x-ray effect so he tried exposing some photographic plates to phosphorescent salts in order to confirm it.
Unsurprisingly, Becquerel also won the Nobel Prize, an award he shared with Pierre and Marie Curie in 1903 Source: WordPress
None of the materials used ended up having an effect, save for one: uranium salts. And even still, that discovery was made completely by chance. Becquerel considered sunlight to be essential to the experiment, and it was cloudy on the day he planned to test the uranium salts. Becquerel stuck everything in a drawer and waited to experiment another day, only to find days later that the uranium salts caused the photographic plate to blacken in spite of the darkness.
The photographic plate blackened by uranium salts Source: Wikipedia
Becquerel had wrapped the plates in paper so they were never in direct contact with the uranium salts, which meant that some unknown form of radiation capable of passing through solid objects was responsible for this event, not phosphorescence. Becquerel had stumbled upon radioactive decay or, as more know it, radioactivity.
