Drift speed of electrons is of the order of ${10^{ - 4}}\,m/\sec $

Davisson and Germer experiment was conducted by two American scientists Clinton Davisson and Lester Germer, in 1927, to verify the de Broglie hypothesis that a material particle posses wave nature. 

The Davisson and Germer experiment consisted of Nickel crystal (target), electron gun and a detector. The electron gun consisted of tungsten filament with high and low tension batteries. The work function of uncoated tungsten filament is 4.5 eV. The coating of Barium oxide on this filament reduces its work function so that electron can be emitted at low temperature.

Davisson-Germer experiment was conducted by two American scientists Clinton Davisson and Lester Germer, in 1927, to verify the de Broglie hypothesis that a material particle posses wave nature. 

Davisson-Germer experiment was conducted by two American scientists Clinton Davisson and Lester Germer, in 1927, to verify the de Broglie hypothesis that a material particle posses wave nature. 

Davisson-Germer experiment was conducted by two American scientists Clinton Davisson and Lester Germer, in 1927, to verify the de Broglie hypothesis that a material particle posses wave nature. They experimentally proved the wave nature of electron through diffraction of electron beam by a nickel crystal.

Kinetic energy of the electron will be due to the voltage supplied.

$\begin{array}{l} nb=2d\sin  \theta  \ \frac { { 12.27 } }{ { \sqrt { 75 }  } } =2d\sin  45 \ 1.41=2d\times \frac { 1 }{ { \sqrt { 2 }  } }  \ \therefore d=\frac { { 1.41 } }{ { 1.41 } } =1A^{ ^{ \circ  } } \end{array}$

Davisson and Germer's actual objective was to study the surface of a piece of nickel by directing a beam of electrons at the surface and observing how many electrons bounced off at various angles. They expected that because of the small size of electrons, even the smoothest crystal surface would be too rough and thus the electron beam would experience diffuse reflection.

During the experiment an accident occurred and air entered the chamber, producing an oxide film on the nickel surface. To remove the oxide, Davisson and Germer heated the specimen in a high temperature oven, not knowing that this affected the formerly polycrystalline structure of the nickel to form large single crystal areas with crystal planes continuous over the width of the electron beam. 

When they started the experiment again and the electrons hit the surface, they were scattered by atoms which originated from crystal planes inside the nickel crystal.In 1925, they generated a diffraction pattern with unexpected peaks.

So, the answer is option (C).

As electron waves oscillation is confined in one orientation only, therefore  it cannot be polarized.

In Davisson-Germer experiment, maximum intensity of diffracted electron beam was found at different angles by varying the applied voltage to the electron gun. The highest intensity was observed at an angle $\phi =50^o$ with a voltage of $54 V$, giving the electron a kinetic energy of $54eV$.

In Davisson -Germer experiment, it was observed that the intensity of the scattered electron beam depends on the scattering angle $\phi$. Also, it Davisson and Germer observed that the maximum intensity was detected when the scattering angle was  $50^o$.

In Davisson-Germer experiment, maximum intensity of diffracted electron beam was found at different angles by varying the applied voltage to the electron gun from $44V$ to $68V$. The highest intensity was observed at an angle $\phi =50^o$ with a voltage of $54 V$, giving the electron a kinetic energy of $54eV$.