Who was the first to verify that electrons are wave-like in nature?

In the Davisson and Germer experiment,the velocity of electrons emitted from the electron gun can be increased by

In the Davisson-Germer experiment,an electron beam of energy $60 \ eV$ is incident normally on a crystal surface. If the maximum intensity is observed at an angle of $50^\circ$ with the direction of the incident beam,what is the interatomic spacing in the crystal lattice in $\mathring A$?

Statement $1$: The Davisson-Germer experiment established the wave nature of electrons. Statement $2$: If electrons possess wave nature,they can undergo interference and diffraction.

The Davisson-Germer experiment that first demonstrated the wave nature of matter used electrons accelerated to $54 \ V$. Determine the wavelength of the electrons in the Davisson-Germer experiment in $\mathring{A}$.

Using the Heisenberg uncertainty principle,arrange the following particles in the order of increasing lowest energy possible.
$(I)$ An electron in $H_{2}$ molecule
$(II)$ $A$ hydrogen atom in a $H_{2}$ molecule
$(III)$ $A$ proton in the carbon nucleus
$(IV)$ $A$ $H_{2}$ molecule within a nanotube