The Schwarzschild black hole under f(R) gravity can exist light ring

For the relationship between the limit $y$ of the incident particle under the preset boundary (${\mu} = {y}{\omega}$), we find the relationship between the black hole thermodynamics and the light ring and use the boundary condition pair to establish y and the relationship between R. A pattern under f(R) gravity, with a possible solution. When y tends to 1. At this time, there is a potential barrier near the event horizon, that is, the Schwarzschild black hole under the gravitational force of f(R) exists a light ring.