Strong gravitational lensing by Schwarzschild black hole
  Schwarzschild black holes can produce strong gravitational lensing. The relativistic images are produced due to bending of light around the black hole. We propose a model equation to study the strong gravitational lensing. The model equation can well describe the bending angle from a range very close to the photon sphere to the first relativistic image. 
Tushar Kanti Dey
gr-qc