Abstract:
Modified gravity theories are of great interest in both observational and theoretical studies.
In this article we study the correlation between the null geodesics in the background of a fourdimensional Einstein-Maxwell-Gauss-Bonnet AdS black hole, a modification of Einstein gravity,
and it’s thermodynamic phase transition. We study the phase structure of the black hole, using the
coexistence and spinodal curves, to understand the phase transition in a extended phase space. The
imprints of this phase transition features are observed in the behaviour of photon orbit radius and
minimum impact parameter with respect to the Hawking temperature and pressure. The change
in these two quantities during the phase transition serve as order parameter which characterises
the critical behaviour. The correlation shows that thermodynamic phase transition can be studied
by observing the effects of strong gravitational field and vice versa.
