  We solve the Dirac equation, which describes charge massless chiral
relativistic carriers in a two-dimensional graphene. We have identified and
analysed a novel pseudospin-dependent scattering effect. We compute the
tunneling conductance and generalize the analytical result in the presence of
the tunable atomic potential of a graphene strip. The absence of back
scattering in graphene is shown to be due to Berry's phase which corresponds to
a sign change of the wave function under a spin rotation of a particle. We use
the transfer matrix approach and find that the electric conductance of doped
graphene increases due to atomic potential fluctuations.
