The GR Schwarzschild Light Launch Angle program simulates the path of light around a black hole using the Schwarzschild metric and allows the user to set the launch angle of the light. It also displays a plot of the effective potential well for the light. The default setting is light with an r-coordinate value of 3.5 and a launch angle of 1.571 (in radians).
GR Schwarzschild Light Launch Angle Program
Quelle. Open Source Physics