Which experiment led to the discovery of neutrons?

Dual behaviour of matter proposed by de Broglie led to the discovery of electron microscope oftenused for the highly magnified images of biological molecules and othér type of material. If the velocity of the electron in this microscope is '1.6 xx 10^6 ms^(-1)', calculate de Broglie wavelength associated with this electron.

The cutting of DNA at specific locations became possible with the discovery of molecular scissors.