$G$ $P$ Thomson experimentally confirmed the existence of matter waves by the phenomenon of:

An electron behaves like a wave because it......

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 .............. $\mathring{A}$

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:

The Davisson-Germer experiment is the direct evidence of

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