  We study gravitational lensing by a class of zero Ricci scalar wormholes
which arise as solutions in a scalar-tensor theory of gravity. An attempt is
made to find a possible link between lensing features, stable/unstable photon
orbits and the energy conditions on the matter required to support these
spacetimes. Our analysis shows (for this class of wormholes) that light rays
always exhibit a positive deflection if the energy conditions are satisfied
(nonexotic matter content). In contrast, if the energy conditions are violated
(exotic matter), the net deflection of a light ray may be positive, negative or
even zero, depending on values of the metric and impact parameters. This
prompts us to introduce a surface defined by a turning point value at which the
net deflection of a light ray is equal to zero, even though we have a curved
spacetime geometry. We argue that the existence of such a surface may be linked
to exotic/energy condition violating matter. Wormholes in modified gravity with
matter satisfying the energy conditions do not seem to have such a zero
deflection surface. Finally, we study strong gravitational lensing briefly and
also look into the formation of Einstein and relativistic Einstein rings. We
conclude with some estimates on the wormhole mass, throat-radius and the
detectability of the Einstein rings.
