  We analyze spin scattering in ballistic transport of electrons through a
ripple at a normal incidence of an electron flow. The model of a ripple
consists of a curved graphene surface in the form of an arc of a circle
connected from the left-hand and right-hand sides to two flat graphene sheets.
At certain conditions the curvature induced spin-orbit coupling creates a
transparent window for incoming electrons with one spin polarization
simultaneously with a backscattering of those with opposite polarization. This
window is equally likely transparent for electrons with spin up and spin down
that move in opposite directions. The spin filtering effect being small in one
ripple becomes prominent with the increase of N consequently connected ripples
that create a graphene sheet of the sinusoidal type. We present the analytical
expressions for spin up (down) transmission probabilities as a function of N
connected ripples.
