What is the phenomenon of radioactivity? How was natural radioactivity discovered?

Radioactivity is the phenomenon of spontaneous transformation of some nuclei into others with the emission of various particles. Henri Becquerel, by blackening the photographic plate, established the fact that uranium salts emitted invisible rays of strong penetrating power.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.