If one assumes that initially the light is far enough from the lens to neglect gravity, the perpendicular distance between the light's initial trajectory and the lens is b (the impact parameter), and the parallel distance is r ∥ ∥ such that r 2 = b 2 + r ∥ ∥ 2 . We additionally assume a constant speed of light along the parallel direction, d r ∥ ∥ ≈ ≈ c d t , and that the light is only being deflected a small amount. After plugging these assumptions into the above equation and further simplifying, one can solve for the velocity boost in the perpendicular direction. The angle of deflection between the corpuscle’s initial and final trajectories is therefore (see, e.g., M. Meneghetti 2021)