In becquerel’s initial experiment, in which he exposed uranium salt crystals to sunlight, the photographic paper became exposed even though it was shaded from the sun by a dark cloth. at first, how did becquerel explain this result? the black cloth emitted gamma rays that exposed the film. the sun emitted gamma rays that exposed the film. the crystals emitted x-rays when they were exposed to light, exposing the film. the crystals phosphoresced when they were exposed to light, exposing the film.

fourth option, the crystals phosphoresced when they were exposed to light, exposing the film.


Justification:

Becquerel experiment was developed to study the phosphoresence: the materials exposed to sunlight are able to emit that absorbed light when the exposition ends and they glow in the dark.

That effect is what he was expecting, predicted and obtained.

Nevertheless, further experimentation, one day in which the samples (crystals) were not exposed to the sunlight, they still were  able to emitt light (exposing the film), so he concluded that the crystals were radiactive (emitted radiation per se)

Compound with sulfer  is bright red