The actual Davisson-Germer experiment (1927) was carried out with the following parameters: the crystal was Nickel, for which the lattice parameter is d = 0.91 ; the electrons were passed through a potential difference of ~ 54 V, i.e. their kinetic energy was about 54 eV. a) Calculate the diffraction angle 0 for which the diffraction maximum is expected to be observed. b) In the actual experiment, Davisson and Germer varied the voltage, i.e. the kinetic energy of the electrons, and observed the wave-like pattern for the scattering intensity as a function of the electron velocity shown in the lecture notes. Explain this wave-like pattern and calculate the position (in terms of the voltage or the electron velocity) of a few expected maxima.