  We address the problem of a Coulomb impurity in graphene in the presence of a
perpendicular uniform magnetic field. We show that the problem can be solved
below the supercritical impurity magnitude within the WKB approximation.
Without impurity the semiclassical energies correctly reproduce the Landau
level spectrum. For a given Landau level the WKB energy depends on the absolute
value of angular momentum in a way which is consistent with the exact
diagonalization result. Below the supercritical impurity magnitude, the WKB
solution can be expanded as a convergent series in powers of the effective fine
structure constant. Relevance of our results to validity of the widely used
Landau level projection approximation is discussed.
