the idea that small particles can act as both waves and particles
Democritus
Ernest Rutherford
Max Planck
Werner Heisenberg
Louis de Brogile
we can't measure the position of an electron and its speed at the same time
Albert Einstien
Albert Einstien observed that if a certian metal plate is hit with light, a electron is ejected
an object that absorbs light at one frequency and then re-emits another