Question

Becquerel’s experiment consisted of four steps.

1. Get a sample of a uranium salt.
2. Expose the salt to sunlight.
3. Expose photographic plates to the salt.
4. Develop the plates.

A change in which step led to Becquerel’s discovery of radioactivity?
1
2
3
4

Answer 1

A change in step 2 of Becquerel's experiment, which involved exposing a uranium salt to sunlight, led to the discovery of radioactivity when he checked the photographic plates that had been stored in darkness and noticed unexpected spots of exposure.

Step-by-step explanation:

The discovery of radioactivity by Henri Becquerel was a result of a change in step 2 of his experiment, which involved exposing a uranium salt to sunlight. Becquerel stumbled upon this phenomenon when, due to overcast weather, he was unable to follow through with his initial plan of exposing the uranium salt to sunlight. Instead, he stored the salts and photographic plates in a dark drawer. When he later developed the plates, which had not been exposed to sunlight, he discovered that the plates were fogged by spots corresponding to the position of the uranium salts. This unexpected outcome led to further experimentation, revealing that the radiation was independent of sunlight or fluorescence, thus uncovering the phenomenon of radioactivity.