  In this work, we study the relation of the eikonal quasinormal modes (EQNMs)
and the unstable fundamental photon orbits (UFPOs) in the Kerr-Newman
spacetime. We find that in the eikonal limit the gravitational and
electromagnetic perturbations of the Kerr-Newman black hole are naturally
decoupled, and a single one-dimensional Schr\"odinger-like equation encoding
the QNM spectrum can be derived. We then show that the decoupled Teukolsky
master equation and the Klein-Gordon equation for the massless scalar field in
the Kerr-Newman spacetime are of the same form in the eikonal limit. As a
direct consequence, taking into account of the boundary conditions for EQNMs we
show an exact correspondence between EQNMs and UFPOs, that is, EQNM/UFPO
correspondence. More precisely, similar to the Kerr case, the real part of
EQNM's frequency is a linear combination of the precessional and (polar)
orbital frequencies, while the imaginary part of the frequency is proportional
to the Lyapunov exponent of the UFPO.
