SAT OwlIn 1896, physicist Henri Becquerel stored uranium salts in a drawer next to photographic plates wrapped in thick black paper. When he developed the plates, he found that they had been exposed, even though they had been kept in the dark the whole time. Because the paper blocked ordinary light, Becquerel reasoned that ______
Which choice most logically completes the text?
the photographic plates must have been defective.
sunlight was needed for the uranium to affect the plates.
black paper produces a faint light of its own.
the uranium salts must give off some kind of radiation that could pass through the paper.
Show answer and explanation
Answer: D
The plates were exposed in a dark drawer, wrapped in paper that blocks light. The only other thing nearby was the uranium, so it must emit something that passes through paper and exposes the plates, as choice D says.
Choice B contradicts the setup; the plates and uranium were kept in the dark, yet the plates were still exposed.
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