  Important classes of null geodesics and hidden symmetries in the Sen black
hole are investigated. First, we obtain the principal null geodesics and
circular photon orbits. Then, an irreducible rank-two Killing tensor and a
conformal Killing tensor are derived, which represent the hidden symmetries.
Analyzing the properties of Killing tensors, we clarify why the Hamilton-Jacobi
and wave equations are separable in this spacetime. We also investigate the
gravitational capture of photons by the Sen black hole and compare the result
with those by the various charged/rotating black holes and naked singularities
in the Kerr-Newman family. For these black holes and naked singularities, we
show the capture regions in a two dimensional impact parameter space (or
equivalently the ``shadows'' observed at infinity) to form a variety of shapes
such as the disk, circle, dot, arc, and their combinations.
