Gravitational lenses do possess a focal point, analogous to traditional lenses, but they are defined by a focal point sphere or horizon rather than a uniform surface. The discussion highlights the complexity of deriving a mass-radius formula for gravitational lenses due to the irregular distribution of mass. While no definitive formula has been established, the concept of a focal horizon is acknowledged as a critical aspect of gravitational lensing. The inquiry suggests a need for further exploration into the mathematical relationships governing these phenomena.
PREREQUISITESAstronomers, astrophysicists, and students of physics interested in gravitational lensing and its mathematical foundations.