[填空题]
For an arsenic donor atom in2nw sytfj 85jvqsq0:35o ta2z a doped silicon semiconductor, assumt1zmp btor8; /e that the "extra" electron moves in a Bohr orbit about the arsenic ion. For this electron in the grb; portz /m18tound state, take into account the dielectric constant $ K = 12 $ of the Si lattice (which represents the weakening of the Coulomb force due to all the other atoms or ions in the lattice), and estimate
(a) the binding energy, E = eV
(b) the orbit radius for this extra electron. r = nm
