In 1896 the French physicist Antoine Henri Becquerel (was) investigating uranium salts. He accidentally left a bit of uranium lying on some photographic plates - glass plates which were used in photography before film was (invented).
(Because*) the plates were wrapped in thick black paper to protect them from light, after some time Becquerel found out that they had been exposed, just as if they had been lying in the sun. He asked himself how this (had) happened. He repeated the experiment and finally (came) to the conclusion that the uranium salt emitted unknown rays, similar (to) X-rays, which could pass through thick black paper. In this way radioactivity (was) discovered.
The story shows some important qualities of a scientist's mind: the desire to understand why something happens the way it does, and the imagination which made Becquerel (think) of a new, original explanation. In 1903, Henri Becquerel won the Nobel (prize) in Physics for his discovery.
1. There is some sour cream, milk, cheese and meat balls in the fridge.
2. There is no paper in the box./ There isn't any paper in the box.
3. There is no sugar in my tea./ There is not any sugar in my tea.
4. Is there any carpet in your room?
5. There is something round on your table.