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

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 ....... $V$.
$(h = 6.6 \times 10^{-34}\; J-s, m = 9.1 \times 10^{-31}\; kg, e = 1.6 \times 10^{-19}\; C)$

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

State Heisenberg's uncertainty principle.

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.