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

The wave nature of electrons suggests that they will produce diffraction effects. Davisson and Germer experimentally proved this by diffracting electrons from a crystal. The law of diffraction from a crystal is obtained from the constructive interference of electron waves reflected from the planes of atoms in the crystal. When electrons are incident on the crystal plane at an angle $i$ with the normal to the plane,and the distance between the planes is $d$,which of the following equations can be used to calculate the de Broglie wavelength of the electrons if a sharp diffraction peak is obtained?

The wave property of electrons implies that they will show diffraction effects. Davisson and Germer demonstrated this by diffracting electrons from crystals. The law governing the diffraction from a crystal is obtained by requiring that electron waves reflected from the planes of atoms in a crystal interfere constructively (see figure).
Electrons accelerated by potential $V$ are diffracted from a crystal. If $d = 1\; \text{\AA}$, and $i = 30^{\circ}$, $V$ should be about ....... $V$.
$(h = 6.6 \times 10^{-34}\; J-s, m = 9.1 \times 10^{-31}\; kg, e = 1.6 \times 10^{-19}\; C)$

In the Davisson-Germer experiment,the nickel crystal acts as a .........

In the Davisson-Germer experiment,an electron beam with a wavelength of $1.5 \ \mathring{A}$ is incident normally on a crystal with an atomic spacing of $3 \ \mathring{A}$. At what angle (in degrees) will the first maximum be formed?

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 $\mathring A$?