Question

In the discovery of radioactivity, why could the darkening of the covered photographic plate NOT be explained by ordinary visible light?

विकल्प

• Because the plate darkened even though the uranium compound was wrapped and kept out of direct light

• Because the uranium compound absorbed all visible light completely

• Because visible light always brightens a photographic plate instead of darkening it

• Because the plate was made of a material that does not respond to light

Answer 1

The photographic plate darkened even when the uranium compound was wrapped and kept out of direct light. Since the substance was shielded from visible light, the effect could not be explained by ordinary visible light, leading to the conclusion that uranium spontaneously emitted invisible, penetrating radiation.