What is Fermi energy? given the number of electrons and (L)

[u061926]

hi every body

question is :
Consider that 5.5E22 free electrons are confined in a potential barrier of length 3.2A . find its Fermi energy ?the main point is that i was confident about the answer of question .. but the doctor said it is wrong .. he said i should use the relation between the number of electrons (N) to the volume (V) to get the density of charge(n) .. Even we learned that this relation used only in 3 dimensions and the question was about potential barrier which is one dimension which means that N=2n and n is fermi level and N is the number of conduction electrons .. am really con fused

 

[Simon Bridge]

Perhaps the doc expected you to interpret the problem for 3D.
As written, it is not well worded.. i.e. particles may be confined in potential wells, not barriers.