The wave nature of electrons was experimentally verified by,

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. Electrons accelerated by a potential $V$ are diffracted by a crystal. If $d = 1 \ \mathring{A}$ and $i = 30^\circ$,then the value of $V$ should be ........... $V$. $(h = 6.6 \times 10^{-34} \ J \cdot s, m_e = 9.1 \times 10^{-31} \ kg, e = 1.6 \times 10^{-19} \ C)$

Match List $-I$ (Experiment performed) with List $-II$ (Phenomena discovered/associated) and select the correct option from the options given below:

List $-I$	List $-II$
$(1)$ Davisson and Germer	$(i)$ Wave nature of electrons
$(2)$ Millikan's oil drop experiment	$(ii)$ Charge of an electron
$(3)$ Rutherford experiment	$(iii)$ Quantisation of energy levels
$(4)$ Franck-Hertz experiment	$(iv)$ Existence of nucleus

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

In the Davisson-Germer experiment,when electrons strike a $Ni$ crystal,which of the following waves are diffracted?

State Heisenberg's uncertainty principle.