Determine the effective focal length of a gravitational lens…
Determine the effective focal length of a gravitational lens created by a celestial object of mass M0 and radius r0 assuming both that dS >> dL, so that rays coming from the source are parallel at the lens, and that tanθ≈θ{“version”:”1.1″,”math”:”tanθ≈θ”} (in radians) for small angles.