Figure 1: GP Thomson Experimental Apparatus and Results
The interference rings in Figure 1 were produced by
sending X-rays of wavelength 
Å ( 
) through a
polycrystalline thin film of copper (interatomic spacing 2.55 Å)
of thickness 
( 
). To produce the same set
of rings but with electrons ( 
) instead of
X-rays, what kinetic energy (in eV) should the electrons
in the incoming beam have?