In general relativity, a point mass deflects a light ray with impact parameter by an angle approximately equal to where G is the gravitational constant, M the mass of the deflecting object and c the speed of light. A naive application of Newtonian gravity can yield exactly half this value, where the light ray is assumed as a massed particle and scattered by the gravitational potential well. This approximation is good when is small. where is the line-of-sight coordinate, and is the vector impact parameter of the actual ray path from the infinitesimal mass located at the coordinates .