Figure 3: Davisson-Germer Apparatus
In a Davisson-Germer experiment, a beam of electrons (each with
momentum 
, mass 
) travels toward
a crystal of inter-planar spacing d=4 Å. (See Figure 3.)
a) Compute the angle 
where there is a strong peak
reflected at an angle which is equal to the angle of incidence, as
shown in the figure.
Hint: In this case it is the scattering off of the different
crystal planes which is important - use the scattering processes
indicated in the figure.