- #1
DGriffiths
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I am interested to know why in any description of electron diffraction apparatus they seem to suggest that the electrons need accelerating up to 5kV (or at least several kV) to show the electron diffraction rings, this seems to give a de Broglie wavelength of around 1.2 x 10^-11m whereas the lattice spacing in a graphite target is of the order of 2 x 10^-10m
Now working back from this to get de Broglie wavelength similar to this lattice spacing gives electron momentum of 3.32 x 10^-24kgm/s, ke of 6.03 x 10^-18J and so we are talking 37.8eV electrons?
Why isn't a 50V supply enough then why the need for 5kV?
Now working back from this to get de Broglie wavelength similar to this lattice spacing gives electron momentum of 3.32 x 10^-24kgm/s, ke of 6.03 x 10^-18J and so we are talking 37.8eV electrons?
Why isn't a 50V supply enough then why the need for 5kV?