Why did Becquerel expose uranium crystals to sunlight in his initial experiment?
He wanted to show that warmed crystals radiate heat.
He wanted to show that the crystals emit X-rays.
He wanted to show that the crystals emit light after absorbing light.
He wanted to show that the crystals would become radioactive when they were exposed to sunlight.

Question

Why did Becquerel expose uranium crystals to sunlight in his initial experiment?
He wanted to show that warmed crystals radiate heat.
He wanted to show that the crystals emit X-rays.
He wanted to show that the crystals emit light after absorbing light.
He wanted to show that the crystals would become radioactive when they were exposed to sunlight.

anonymous · Answer

do u have an answer

whpalmer4 · Answer

Becquerel wanted to show that crystals emit x-rays after absorbing light, which would explain the patterns seen on the photographic plates exposed to  uranium salts.  However, one fateful day he was unable to expose the plates he prepared due to a lack of sunlight, and discovered that the same patterns could be seen after development, which indicated that sunlight was not an essential element, and that something intrinsic to the uranium was exposing the photographic emulsions.

Just so happens I read an account of this experiment in the book "Uranium: War, Energy, and the Rock that Shaped the World" in the last few days :-)