Past exam of the relativity course of the University of Cambridge / 2022 / Section A / 3

For a grazing null geodesic, take the impact parameter as $b\simeq R=6.0\times 10^6\mathrm{m}$. The leading Schwarzschild light deflection isWith the gravitational constant $G\simeq 6.6743\times 10^{-11}{\mathrm{m}}^3\mathrm{k}{\mathrm{g}}^{-1}{\mathrm{s}}^{-2}$ and speed of light $c\simeq 2.998\times 10^8\mathrm{m}{\mathrm{s}}^{-1}$,Here $GM/(R{c}^2)\simeq 2.5\times 10^{-4}\ll 1$, so the weak-field approximation is appropriate. A ray passing at a larger impact parameter has a correspondingly smaller deflection.