Lattice forces affect the motion of electrons in a metallic crystal, so that the relationship between the energy E and wave number k is not the classical equation E = k/2m, where m is the electron mass. Instead, it is possible to use an effective mass m* given by which of the following? dk A. m = 1 (1) dE k B. m () C. m/hm ( dE2 D. m. dk 1/3 dk Em = Am (d)