$A$ sodium atom is in one of the states labeled 'Lowest excited levels'. It remains in that state for an average time of $10^{-8} \, s$,before it makes a transition back to a ground state. What is the uncertainty in energy of that excited state?

In the Davisson-Germer experiment,an electron beam of energy $75 \ eV$ falls normally on the surface of a crystal. If the maximum intensity is obtained at an angle of $45^o$ to the direction of the incident beam,then the inter-atomic distance in the lattice plane of the crystal will be .............. $\mathring{A}$

The wave nature of electrons was experimentally verified by,

This question has Statement-$1$ and Statement-$2$. Of the four choices given after the Statements,choose the one that best describes the two Statements.
Statement-$1$: Davisson-Germer experiment established the wave nature of electrons.
Statement-$2$: If electrons have wave nature,they can interfere and show diffraction.

Given below are two statements :-
Statement $I$ : Davisson-Germer experiment establishes the wave nature of electrons.
Statement $II$ : If electrons have wave nature,they can interfere and show diffraction.
In the light of the above statements,choose the correct answer from the options given below:

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A:$ The beam of electrons shows wave nature and exhibits interference and diffraction.
Reason $R:$ Davisson-Germer experimentally verified the wave nature of electrons.
In the light of the above statements,choose the most appropriate answer from the options given below: