Radiation

Discovery of the nucleus:

Alpha particles from a radioactive source were allowed to strike a thin gold foil. Alpha particles produce a tiny, but visible flash of light when they strike a fluorescent screen. Surprisingly, alpha particles were found at large deflection angles and some were even found to be back-scattered. 

Most alpha particles went straight through the foil. Only about 1 in 2000 were deflected.

1 in 10000 particles were deflected more than 90 degrees. 

This experiment showed that the positive matter in atoms was concentrated in an incredibly small…